sentences:  by 1888.A cog is a tooth on a wheel.From Middle English cogge, from Old Norse (compare Norwegian "kugg" ('cog'), Swedish "kugg", "kugge" ('cog, tooth')), from Proto-Germanic *"kuggō" (compare Dutch "kogge" ('cogboat'), German "Kock"), from Proto-Indo-European *"gugā" ('hump, ball') (compare Lithuanian "gugà" ('pommel, hump, hill'), from PIE *"gēw-" ('to bend, arch').