Bug

Bug
1. A bugbear; anything which terrifies. Sir, spare your threats: The bug which you would fright me with i seek. (Shak)
2. (Science: zoology) a general name applied to various insects belonging to the Hemiptera; as, the squash bug; the chinch bug, etc.
3. (Science: zoology) An insect of the genus Cimex, especially the bedbug (c. Lectularius). See bedbug.
4. (Science: zoology) One of various species of Coleoptera; as, the ladybug; potato bug, etc.; loosely, any beetle.
5. (Science: zoology) One of certain kinds of Crustacea; as, the sow bug; pill bug; bait bug; salve bug, etc.
According to present popular usage in England, and among housekeepers in America, bug, when not joined with some qualifying word, is used specifically for bedbug. As a general term it is used very loosely in America, and was formerly used still more loosely in England. God’s rare workmanship in the ant, the poorest bug that creeps. . This bug with gilded wings. . Bait bug. See bait. Bug word, swaggering or threatening language.
Origin: oe. Bugge, fr. W. Bwg, bwgan, hobgoblin, scarecrow, bugbear. Cf. Bogey, Boggle.