1730-40, Americanism; lady (uninflected possessive case) Virgin Mary + bird; i.e. (our) Lady's bird
[ley-dee-buhg] /ˈleɪ diˌbʌg/
any of numerous small, round, often brightly colored and spotted beetles of the family Coccinellidae, feeding chiefly on aphids and other small insects, but including several forms that feed on plants.
any of various small brightly coloured beetles of the family Coccinellidae, such as Adalia bipunctata (two-spotted ladybird), which has red elytra marked with black spots Usual US and Canadian name ladybug
1690s, from lady + bug. The "lady" is the Virgin Mary (cf. Ger. cognate Marienkäfer). In Britain, now usually ladybird beetle (1704), through aversion to the word bug, which there has overtones of sodomy.