What is the X in X-mas?
Old English is "ice" (also the name of the rune for -i-), from Proto-Germanic *isa- (cf. Old Norse iss, Old Frisian is, Dutch ijs, German Eis), with no certain cognates beyond Germanic, though possible relatives are Avestan aexa- "frost, ice," isu- "frosty, icy;" Afghan asai "frost." Slang meaning "diamonds" is attested from 1906.
Ice cube attested from 1904. Ice age attested from 1832. To break the ice "to make the first opening to any attempt" is from 1580s, metaphoric of making passages for boats by breaking up river ice though in modern use usually with implications of "cold reserve."
To remove the tension at a first meeting, at the opening of a party, etc.: “That joke really broke the ice at the conference; we all relaxed afterward.”
To dissipate the sense of strain among people who do not know each other: I broke the ice by saying she looked like Charlemagne's mother (late 1500s+)
Excellent; fine; cool (1960s+ Cool talk)noun
frequently mentioned (Job 6:16; 38:29; Ps. 147:17, etc.). (See CRYSTAL.)