honeydew n.

Middle English hony, from Old English hunig "honey," from Proto-Germanic *hunang- (source also of Old Norse hunang, Swedish honung, Old Saxon honeg, Old Frisian hunig, Middle Dutch honich, Dutch honig, Old High German honang, German Honig "honey"), of uncertain origin. Perhaps from a PIE *k(e)neko- denoting yellow, golden, or brownish colors (compare Sanskrit kancan- "golden," Welsh canecon "gold," Greek knēkos "yellowish"), or perhaps from a substratum word. Finnish hunaja is a Germanic loan-word.

The more common Indo-European word is represented in Germanic by the Gothic word for "honey," miliþ (from PIE root *melit- "honey"). A term of endearment from at least mid-14c.; extended form honey-bunch attested by 1904. Meaning "anything good of its kind" is 1888, American English. Honey-locust, North American tree, so called from 1743, said to be named from a sweet pulp made by Native Americans from the tree's beans.

"water vapor deposited from the atmosphere by condensation, especially during the night," Middle English deaw, deu, from Old English deaw, from Proto-Germanic *dawwaz (source also of Old Saxon dau, Old Frisian daw, Middle Dutch dau, Old High German tau, German Tau, Old Norse dögg "dew"), perhaps from PIE root *dheu- "to flow" (source also of Sanskrit dhavate "flows, runs").

Used figuratively of something refreshing (late Old English), or suggestive of morning and youthful freshness (1530s). As a verb, "to wet with or as with dew," Old English deawian.

The formation of dew is explained by the loss of heat by bodies on the earth's surface through radiation at night, by which means they and the air immediately about them are cooled below the dew-point ....Dew is thus deposited chiefly on bodies which are good radiators and poor conductors of heat, like grass; hence also it appears chiefly on calm and clear nights--that is, when the conditions are most favorable for radiation. It never appears on nights both cloudy and windy. In winter dew becomes hoar frost. [Century Dictionary]