英语词源字典 - 在线词源网站

apologetic (adj.)[apologetic 词源字典]: 1640s, "vindicatory," from French apologétique, from Latin apologeticus, from Greek apologetikos "defensible," from apologeisthai (see apology). Meaning "regretfully acknowledging failure" is from 1855. As a noun, "formal defense," from early 15c. Related: Apologetics (c. 1753).[apologetic etymology, apologetic origin, 英语词源]
apologize (v.): 1590s, "to speak in defense of;" see apology + -ize. Main modern sense "to regretfully acknowledge" is attested by 1725. The Greek equivalent, apologizesthai, meant simply "to give an account." Related: Apologized; apologizing.
frog (n.1): Old English frogga "frog," a diminutive of frosc, forsc, frox "frog," a common Germanic word but with different formations that are difficult to explain (cognates: Old Norse froskr, Middle Dutch vorsc, German Frosch "frog"), probably literally "hopper," from PIE root *preu- "to hop" (cognates: Sanskrit provate "hops," Russian prygat "to hop, jump"). Watkins calls the Old English -gga an "obscure expressive suffix."

The Latin word for it (rana) is imitative of croaking. Also in Middle English as frok, vrogge, frugge, and with sometimes plural form froggen. Collateral Middle English forms frude, froud are from Old Norse frauðr "frog," and native alternative form frosk "frog" survived in English dialects into the 19c.
I always eat fricasseed frogs regretfully; they remind one so much of miniature human thighs, and make one feel cannibalistic and horrid .... [H. Ellen Brown, "A Girl's Wanderings in Hungary," 1896]
As a British derogatory term for "Frenchman," 1778 (short for frog-eater), but before that (1650s) it meant "Dutch" (from frog-land "marshy land," in reference to their country). To have a frog in the throat "be hoarse" is from 1892, from frog as a name for a lump or swelling in the mouth (1650s) or throat infections causing a croaking sound.
regretful (adj.): 1640s, "full of regret," from regret + -ful. Regretfully, properly "with regret," incorrectly used in place of regrettably "it is to be regretted that; calling for regret" since at least 1965. "A regrettable use, prob. after HOPEFULLY adv.2" [OED].