1769, of words, expressions, etc., "point, sharpness, power of irritation;" see poignant + -ance. As "power of stimulating the organs of taste" by 1782; in reference to emotional states, "painfulness, bitterness" by 1812.
late 14c., poinaunt, "painful to physical or mental feeling" (of sauce, spice, wine as well as things that affect the feelings), from Old French poignant "sharp, pointed" (13c.), present participle of poindre "to prick, sting," from Latin pungere "to prick, pierce, sting," figuratively, "to vex, grieve, trouble, afflict" (from suffixed form of PIE root *peuk- "to prick"). Related: Poignantly.
The sense of "sharp to the taste" is now obsolete. The word contains an etymological double-reverse. Latin pungere is from the same root as Latin pugnus "fist," and represents a Latin metathesis of -n- and -g- that was reversed in French.
word-forming element attached to verbs to form abstract nouns of process or fact (convergence from converge), or of state or quality (absence from absent); ultimately from Latin -antia and -entia, which depended on the vowel in the stem word, from PIE *-nt-, adjectival suffix.
Latin present-participle endings for verbs stems in -a- were distinguished from those in -i- and -e-. Hence Modern English protestant, opponent, obedient from Latin protestare, opponere, obedire.
As Old French evolved from Latin, these were leveled to -ance, but later French borrowings from Latin (some of them subsequently passed to English) used the appropriate Latin form of the ending, as did words borrowed by English directly from Latin (diligence,absence).
English thus inherited a confused mass of words from French (crescent/croissant), and further confused it since c. 1500 by restoring -ence selectively in some forms of these words to conform with Latin. Thus dependant, but independence, etc.