Old English hamor "hammer," from Proto-Germanic *hamaraz (source also of Old Saxon hamur, Middle Dutch, Dutch hamer, Old High German hamar, German Hammer). The Old Norse cognate hamarr meant "stone, crag" (it's common in English place names), and suggests an original sense of the Germanic words as "tool with a stone head," which would describe the first hammers. The Germanic words thus could be from a PIE *ka-mer-, with reversal of initial sounds, from PIE *akmen "stone, sharp stone used as a tool" (source also of Old Church Slavonic kamy, Russian kameni "stone"), from root *ak- "be sharp, rise (out) to a point, pierce."
As a part of a firearm, 1580s; as a part of a piano, 1774; as a small bone of the ear, 1610s. Figurative use of "aggressive and destructive foe" is late 14c., from similar use of French martel, Latin malleus. To go at it hammer and tongs "with great violence and vigor" (1708) is an image from blacksmithing (the tongs hold the metal and the hammer beats it). Hammer and sickle as an emblem of Soviet communism attested from 1921, symbolizing industrial and agricultural labor.
late 14c., "deal blows with a hammer or axe;" mid-15c., "to produce (something) by blows with a hammer," from hammer (n.). Also sometimes in Middle English the verb to describe how Christ was crucified. Figurative meaning "work (something) out laboriously" recorded from 1580s. Meaning "beat or drive with or as if with a hammer" is from 1640s; that of "to defeat heavily" is from 1948. Old English had hamorian "to beat out, forge." Related: Hammered; hammering.
Crist, as he was ruthfully hamerd apon the croce, Songe to his fadire of heven.
["The Mirror of Man's Salvation," 15c.]
also hammer-head, 1560s, "head of a hammer," from hammer (n.) + head (n.). From 1796 (American English) in reference to a kind of shark, so called for its broad, transverse head. The animal is referred to as hammer-headed shark from 1752 and hammer-fish from 1745. The older name for it was balance-fish; there was a full specimen and a head of another under that name in the Royal Society Museum by 1681:
He hath his Name not unaptly from the ſhape of his Head, very different from that of all other Fiſhes, being ſpread out horizontally, like the Beam of a Balance; his eyes ſtanding at the two extremes, as the iron Hooks do at the end of the Beam. He grows sometimes to the length of four or five yards: but this is a young one. [Nehemiah Grew, M.D., "Catalogue & Deſcription Of the Natural and Artificial Rarities Belonging to the Royal Society And preſerved at Greſham Colledge. Whereunto is Subjoyned the Comparative Anatomy of Stomachs and Guts. By the ſame author" London, 1681 ]
Compare French requin marteau, Italian pesce martello, etc. The Greeks named it for the cross-bar of a yoke (zygon) and called it zygania. "According to Xenocrates, and to Philotinus ap. Galen vi. 727, it is tough and indigestible, but may be eaten pickled" [Thompson].
It forms all or part of: acacia; acanthus; accipiter; acer; acerbic; acerbity; acervate; acervulus; acescent; acetic; acid; acicular; acme; acne; acrid; acridity; acrimony; acro-; acrobat; acromegaly; acronym; acrophobia; acropolis; acrostic; acrylic; acuity; aculeate; acumen; acupressure; acupuncture; acute; aglet; ague; Akron; anoxic; awn; coelacanth; dioxin; deoxy-; eager; ear (n.2) "grain part of corn;" edge (n.); egg (v.) "to goad on, incite;" eglantine; epoxy; ester; exacerbation; hammer; hypoxia; mediocre; oxalic; oxide; oxy-; oxygen; oxymoron; paragon; pyracanth; paroxysm; selvage; vinegar.
It is the hypothetical source of/evidence for its existence is provided by: Greek akros "at the end, at the top, outermost; consummate, excellent," akis "sharp point," akros "at the farthest point, highest, outermost," akantha "thorn," akme "summit, edge," oxys "sharp, bitter;" Sanskrit acri- "corner, edge," acani- "point of an arrow," asrih "edge;" Oscan akrid (ablative singular) "sharply;" Latin acer (fem. acris) "sharp to the senses, pungent, bitter, eager, fierce," acutus "sharp, pointed," acuere "to sharpen," acerbus "harsh, bitter," acere "be sharp, be bitter," acus "a needle, pin," ocris "jagged mountain;" Lithuanian ašmuo "sharpness," akstis "sharp stick;" Old Lithuanian aštras, Lithuanian aštrus "sharp;" Old Church Slavonic ostru, Russian óstryj "sharp;" Old Irish er "high;" Welsh ochr "edge, corner, border;" Old Norse eggja "goad;" Old English ecg "sword;" German Eck "corner."
c. 1200, mealle, "heavy wooden hammer or mallet; sledgehammer," from Old French mail "hammer," from Latin malleus "hammer" (from PIE root *mele- "to crush, grind").