c. 1400, "belonging to (religious) ritual," also as a noun, "a ceremonial practice," from Late Latin caerimonialis "pertaining to ceremony," from caerimonia (see ceremony). Related: Ceremonially.
Ceremonial means connected with or constituting or consisting of or fit for a ceremony (i.e. a piece of ritual or formality) or ceremonies .... Ceremonious means full of or resulting from ceremony i.e. attention to forms .... [Fowler]
mid-15c., occasionen, "to bring (something) about, be the cause of (something)," from occasion (n.), or else from Old French occasionner "to cause," from Medieval Latin occasionare, from Latin occasionem (see occasion (n.)). Related: Occasioned; occasioning.
late 14c., occasioun, "opportunity; grounds for action or feeling; state of affairs that makes something else possible; a happening, occurrence leading to some result," from Old French ochaison, ocasion "cause, reason, excuse, pretext; opportunity" (13c.) or directly from Latin occasionem (nominative occasio) "opportunity, appropriate time," in Late Latin "cause," from occasum, occasus, past participle of occidere "fall down, go down," from ob "down, away" (see ob-) + -cidere, combining form of cadere "to fall" (from PIE root *kad- "to fall"). The notion is of a "falling together," or juncture, of circumstances. The sense of "the time or a time at which something happens" is from 1560s.
type of bread, usually braided, typically eaten on Jewish ceremonial occasions, 1887, from Yiddish khale, from Hebrew chala, which is possibly from hll "hollow, pierce," and perhaps is a reference to the original appearance of it.