cog

Inherited from Middle English cogge, from Old Norse *kogge, *koggr (see Old Swedish kogge, kogger), from Proto-Germanic *kuggō (“cog, swelling”), from Proto-Indo-European *gugā (“hump, ball”), from *gēw- (“to bend, arch”). Compare Lithuanian gugà (“pommel, hump, hill”).

Cognates includes: Swedish kugg, kugge (“cog tooth”), Norwegian kugg (“cog”). The meaning of “cog” in carpentry derives from association with a tooth on a cogwheel. Compare Old Swedish koggavidher (“cog wood”), “wood reserved for a millwheel”.

See also dialectal English cag (“stump”), keg; Old Norse kaggi (“keg”) +‎ -gi (diminutive suffix), from the Germanic base *kagô (“bush, branch, stalk, stump”); also found in Bavarian Kag (“the stalk or stem of a cabbage”); dialectal Swedish kage (“treestump; piece of wood; post”), kagg or kagge (“scythe handle”); Norwegian Nynorsk kage or kagge (“low lying bush, small tree”), dialectal kagg (“scythe handle”); Old English ċeacga (“broom, furze, gorse”), whence English chag (“branch”), also Old English cyċġel, English cudgel (“knotty club”). The ultimate origin could be related to English cog (“cargo boat”) (Dutch kogge), probably named for its “round swollen” appearance.

Uncertain. Both verb and noun appear first in 1532.