Etymology
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fortitude (n.)

late 14c., "moral strength (as a cardinal virtue); courage," from Latin fortitudo "strength, force, firmness, manliness," from fortis "strong, brave" (see fort). From early 15c. as "physical strength."

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fortitudinous (adj.)
"capable of endurance," 1752, from Latin fortitudinem (nominative fortitudo) "strength, firmness" (see fortitude) + -ous. Related: Fortitudinously.
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powerless (adj.)

early 15c., pouerles, "lacking might or fortitude," from power (n.) + -less. Related: Powerlessly; powerlessness.

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pusillanimity (n.)

late 14c., pusillanimite, "timidity, faint-heartedness, lack of the spirit of courage or fortitude," from Old French pusillanimité (14c.) and directly from Church Latin pusillanimitatem (nominative pusillanimitas) "faint-heartedness," from Latin pusillanimis "faint-hearted, having little courage" (see pusillanimous).

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nervy (adj.)

c. 1600, "vigorous, sinewy, strong," from nerve (n.) + -y (2). By 1870 as "full of courage or fortitude;" by 1891 as "excitable;" by 1896 as "coolly impudent." Related: Nerviness.

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strength (n.)
Old English strengþu, strengð "bodily power, force, vigor, firmness, fortitude, manhood, violence, moral resistance," from Proto-Germanic *strangitho (source also of Old High German strengida "strength"), from PIE *strenk- "tight, narrow" (see string (n.)), with Proto-Germanic abstract noun suffix *-itho (see -th (2)). Compare length/long. From the same root as strong,
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tolerance (n.)
early 15c., "endurance, fortitude" (in the face of pain, hardship, etc.), from Old French tolerance (14c.), from Latin tolerantia "a bearing, supporting, endurance," from tolerans, present participle of tolerare "to bear, endure, tolerate" (see toleration). Of individuals, with the sense "tendency to be free from bigotry or severity in judging other," from 1765. Meaning "allowable amount of variation" dates from 1868; and physiological sense of "ability to take large doses" first recorded 1875.
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force (n.)
c. 1300, "physical strength," from Old French force "force, strength; courage, fortitude; violence, power, compulsion" (12c.), from Vulgar Latin *fortia (source also of Old Spanish forzo, Spanish fuerza, Italian forza), noun use of neuter plural of Latin fortis "strong, mighty; firm, steadfast; brave, bold" (see fort).

Meanings "power to convince the mind" and "power exerted against will or consent" are from mid-14c. Meaning "body of armed men, a military organization" first recorded late 14c. (also in Old French). Physics sense is from 1660s; force field attested by 1920. Related: Forces.
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virtue (n.)
Origin and meaning of virtue

c. 1200, vertu, "moral life and conduct; a particular moral excellence," from Anglo-French and Old French vertu "force, strength, vigor; moral strength; qualities, abilities" (10c. in Old French), from Latin virtutem (nominative virtus) "moral strength, high character, goodness; manliness; valor, bravery, courage (in war); excellence, worth," from vir "man" (from PIE root *wi-ro- "man").

For my part I honour with the name of virtue the habit of acting in a way troublesome to oneself and useful to others. [Stendhal "de l'Amour," 1822]

Especially (in women) "chastity, sexual purity" from 1590s. Phrase by virtue of (early 13c.) preserves alternative Middle English sense of "efficacy." Wyclif Bible has virtue where KJV uses power. The seven cardinal virtues (early 14c.) were divided into the natural (justice, prudence, temperance, fortitude) and the theological (hope, faith, charity). To make a virtue of a necessity (late 14c.) translates Latin facere de necessitate virtutem [Jerome].

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cardinal (adj.)
Origin and meaning of cardinal

"chief, pivotal," early 14c., from Latin cardinalis "principal, chief, essential," a figurative use, literally "pertaining to a hinge," from cardo (genitive cardinis) "that on which something turns or depends; pole of the sky," originally "door hinge," which is of unknown origin. Related: Cardinally.

The cardinal numbers (1590s) are "one, two, three," etc. as opposed to ordinal numbers "first, second, third," etc.; they are so called because they are the principal numbers and the ordinals depend on them.

The cardinal points (1540s) are north, south, east, west. The cardinal sins (c. 1600) are too well known to require rehearsal. The cardinal virtues (c. 1300) were divided into natural (justice, prudence, temperance, fortitude) and theological (faith, hope, charity). The natural ones were the original classical ones, which were amended by Christians. But typically in Middle English only the first four were counted as the cardinal virtues:

Of þe uour uirtues cardinales spekeþ moche þe yealde philosofes. ["Ayenbite of Inwyt," c. 1340]

By analogy of this, and cardinal winds (late 14c.), cardinal signs (four zodiacal signs marking the equinoxes and the solstices, late 14c.), etc., the adjective in Middle English acquired an association with the number four.

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