[ME. cogge, found from 13th c.: the Sw. kugge, Norw. kug, pl. kugger, in same sense, are evidently cognate; but the relations between them are not determined.
The Celtic words, Ir., Gael. cog, Welsh cocas, uncritically cited as the prob. source, are (as usual in such cases) from English. Derivation from the Romanic family of F. coche, ONF. *coque, Pr. coca, It. cocca ‘notch,’ of which the sense has been considered allied, is phonetically untenable.]
1. One of a series of teeth or similar projections on the circumference of a wheel, or the side of a bar, etc., which, by engaging with corresponding projections on another wheel, etc., transmit or receive motion.
Cogs are either separate wooden pieces attached by mortices and the like, or are cut out of the substance of the wheel, or cast in one with it. The name was probably first given to the wooden pins inserted sideways into the rim of a wheel, which caught the rungs or trundles of a lantern-wheel; hence cog and round, a mechanical arrangement of this type. Hunting cog: in cogged wheels which have a certain proportion to each other, an extra cog given to the larger, by which there is secured a continuous change of cogs engaging with each other and consequently equal wear.
a. 1250. Owl & Night., 86. I-cundure to one frogge, Þat sit at mulne under cogge. [The precise sense here is doubtful.]
1381. Durham Halm. Rolls, I. 170. Præd. Will. inveniet velas, cogges [of a wind-mill].
c. 1440. Promp. Parv., 85. Cogge of a mylle, scarioballum.
1509. Hawes, Past. Pleas., XXVI. xii. (1845), 117. A great whele made by craftly Geometry, Wyth many cogges.
1523. Fitzherb., Husb., § 134. To sell … the crabbe-trees to myllers, to make cogges and ronges.
1627–77. Feltham, Resolves, I. lxviii. 104. Thou canst not sit upon so high a Cog, but maist with turning prove the lowest in the wheel.
1660. R. D’Acres, Elem. Water-drawing, 13. Great wooden wheels with Coggs in them, working Trundles with round staves in them.
1731. Beighton, in Phil. Trans., XXXVII. 6. A Cog-Wheel of 51 Cogs, into which the Trundle V, of six Rounds, works.
1816. J. Smith, Panorama Sci. & Art, I. 314. In large works, where the wheels are of wood, and the teeth are separate pieces morticed into the rim, they are called cogs.
1822. Imison, Sc. & Art (Webster), I. 78. A skilful mill-wright will always give the wheel what he calls a hunting cog.
1868. Lockyer, Elem. Astron., 193. The principle of both clocks and watches is that a number of wheels, locked together by cogs, are forced to turn round.
fig. c. 1640. [Shirley], Capt. Underw., III. iii. in Bullen, O. Pl., II. 372. How will his tongue run when his Coggs are oild.
† b. A float-board. Perhaps only a mistake.
1695. Kennett, Par. Antiq., Gloss. s.v. Cock-boat, The coges or cogs of a mill-wheel, are those slobs or broad pieces of board, that like cogs or boats are drove along by the stream, and so turn round the wheel, and axis, and stones.
2. Short for: a. The series of cogs round a wheel (obs.); b. a cog-wheel.
1712. trans. Pomet’s Hist. Drugs, I. 54. The great Roller in the middle is surrounded with a Cog.
1883. E. Ingersoll, in Harper’s Mag., Jan., 198/2. A stubby black boiler, with a trifling amount of upper gear, makes steam, turning four small wheels by means of a cog underneath.
3. One of the short handles of the pole of a scythe. dial.
1688. R. Holme, Armoury, III. viii. 322. The koggs are the handles on the sythe.
1879. Miss Jackson, Shropsh. Word-bk., s.v. Cleat, ‘The cogs o’ this sned binna-d-as tight as they oughten to be.’
4. (See quot.) dial.
1880. Antrim & Down Gloss., Cog, a wedge or support fixed under anything to steady it.
5. Mining. A block used in building up a support for the roof of a mine; = CHOCK sb.1 4.
1881. Raymond, Mining Gloss., Cogs are not squared, but simply notched where they cross each other.
6. Comb. cog-hole, a place for keeping spare cogs; cog-rail, a toothed rail used in railways with very steep gradients. Also COG-WHEEL.
1733. Derby Mercury, I. No. 52, 1/2. The Boy who killed his Brother, run away and hid himself in the Coghole of the Mill.
