"small village" (Scottish and Irish), early 15c., from Gaelic clach (plural clachan) "stone," originally perhaps "a stone circle."
late 14c., in geometry, "chord of a circle or sphere which passes through its center; the length of a diameter," from Old French diametre, from Latin diametrus, from Greek diametros (gramme) "diagonal of a circle," from dia "across, through" (see dia-) + metron "a measure" (from PIE root *me- (2) "to measure").
"song in which a line or refrain is continually repeated," 1570s, from French rondelet, diminutive of rondel "short poem with a refrain," literally "small circle," diminutive of Old French rond "circle, sphere," originally an adjective from roont (see round (adj.), and compare rondel). With spelling assimilated to lay (n.1) "poem to be sung."