sacred:  Sacred is one of a wide range of English words that go back to Latin sacer ‘sacred, holy’ (which itself came from the same base that produced Latin sancīre ‘consecrate’, source of English saint, sanctuary, etc). Many of them come via the derived verb sacrāre ‘consecrate’. These include consecrate , execrate , sacrament , and sacred itself, which was originally the past participle of the now obsolete verb sacre ‘consecrate’, a descendant via Old French sacrer of Latin sacrāre.
Amongst other relatives are sacerdotal  (from Latin sacerdōs ‘priest’, a derivative of the same base as sacer), sacrifice  (from a Latin compound meaning ‘make holy’), sacrilege  (from a Latin compound meaning ‘steal holy things’), sacristan and its more heavily disguised relative sexton, sacrosanct  (etymologically ‘consecrated with religious ceremonies’), and sacrum ‘bottom section of the spine’  (short for medieval Latin os sacrum ‘holy bone’, which was a direct translation of Greek hieron ostéon, an allusion to the use of the bone in sacrificial ceremonies). => consecrate, execrate, sacrament, sacrifice, sacristan, saint, sanctuary, sexton
late 14c., past participle adjective from obsolete verb sacren "to make holy" (c. 1200), from Old French sacrer "consecrate, anoint, dedicate" (12c.) or directly from Latin sacrare "to make sacred, consecrate; hold sacred; immortalize; set apart, dedicate," from sacer (genitive sacri) "sacred, dedicated, holy, accursed," from Old Latin saceres, from PIE root *sak- "to sanctify." Buck groups it with Oscan sakrim, Umbrian sacra and calls it "a distinctive Italic group, without any clear outside connections." Related: Sacredness.
Nasalized form is sancire "make sacred, confirm, ratify, ordain." An Old English word for "sacred" was godcund. Sacred cow "object of Hindu veneration," is from 1891; figurative sense of "one who must not be criticized" is first recorded 1910, reflecting Western views of Hinduism. Sacred Heart "the heart of Jesus as an object of religious veneration" is from 1765.