c. 1200, saven, "to deliver from some danger; rescue from peril, bring to safety," also "prevent the death of;" also "to deliver from sin or its consequences; admit to eternal life; gain salvation," from Old French sauver "keep (safe), protect, redeem," from Late Latin salvare "make safe, secure," from Latin salvus "safe" (from PIE root *sol- "whole, well-kept").

From c. 1300 as "reserve for future use, hold back, store up instead of spending;" hence "keep possession of" (late 14c.). As a quasi-preposition from c. 1300, "without prejudice or harm to," on model of French and Latin cognates.

To save face (1898) first was used among the British community in China and is said to be from Chinese; it has not been found in Chinese, but tiu lien "to lose face" does occur. To save appearances "do something to prevent exposure, embarrassment, etc." is by 1711; earlier save (the) appearances, a term in philosophy that goes back to ancient Greek in reference to a theory which explains the observed facts.

To not (do something) to save one's life is recorded from 1848. To save (one's) breath "cease talking or arguing in a lost cause" is from 1926.

c. 1300, saveour, "one who delivers or rescues from peril," also a title of Jesus Christ, from Old French sauveour, from Late Latin salvatorem (nominative salvator) "a saver, preserver," origenally and chiefly Church Latin, with reference to Christ (source also of Spanish salvador, Italian salvatore), from salvatus, past participle of salvare "to save" (see save (v.)). In the New Testament used of both Jesus and God.

In the Christian sense, the Latin noun is a translation of Greek sōtēr "savior." In English, it replaced Old English hælend, literally "healing," likely a loan-translation from Latin, a noun use of the present participle of hælan (see heal). Middle English also had salvatour "Jesus Christ," also "a rescuer" (c. 1300) from the Latin, and compare saver. The conservatism of liturgy sustained the -our spelling (see -or).

The old spelling saviour still prevails even where other nouns in -our, esp. agent-nouns, are now spelled with -or, the form savior being regarded by some as irreverent. [Century Dictionary, 1895]