Meaning

noun a request to be present

noun an order to appear in person at a given place and time

noun a writ issued by authority of law; usually compels the defendant's attendance in a civil suit; failure to appear results in a default judgment against the defendant

originFrom Middle English somouns (“order or command to do something”), borrowed from Old French sumunce (modern French semonce), from Vulgar Latin *summonsa, a noun use of the feminine past participle of summoneō, summonēre (“to summon”).

Etymology from Wiktionary, CC BY-SA 3.0