aphid (n.)
1849, Englished from Modern Latin aphides, plural of aphis, coined by Linnaeus (1758), though where he got it and why he applied it to the plant louse are mysteries. The theory favored by OED as "least improbable" is that it derives from the plural of Greek apheides "unsparing, lavishly bestowed," in reference either to the "prodigious rate of production" of the insects or their voracity. The colloquial name was ant-cow (1847). Related: Aphidian (1855).