Entries linking to s.a.
c. 1300, sauns, saun, "without" (mid-12c. in surnames), from Old French san, sans, sen, senz (some of the forms with adverbial genitive -s) "without, except, apart, not counting." This is cognate with Provençal senes, Old Catalan senes, Old Spanish sen (Spanish sin), Old Italian sen, all from Vulgar Latin *sene, from Latin sine "without," an enlarged form of sed, se "without" (from PIE root *sen(e)- "apart, separated;" see sunder).
"A French word which has existed long in English without becoming naturalized; now archaic or affected, except as used in heraldry ..." [Century Dictionary, 1891]; OED writes that the words limited modern use is "chiefly with reminiscence of Shakespere," which it spells that way. In reference to fonts, by 1927, short for sans-serif. Sans souci, French, as an adverbial phrase "free from care, without care or concern," was the name of Frederick the Great's royal palace at Potsdam.
This is reconstructed to be from Proto-Italic *atno- "year" (compare Oscan akno- "year, holiday, time of offering"), from PIE *at-no- "which goes," also "a year" (as "going around"), suffixed form of root *at- "to go" (source also of Sanskrit atati "goes, wanders," atamana- "to travel, wander," atya- "steed, runner"). The root also has Germanic derivatives meaning "a year," such as Gothic aþnam (dative plural) "year."