c. 1100, "celebration of public religious worship according to prescribed forms or methods," from Old French servise "act of homage; servitude; service at table; Mass, church ceremony," from Latin servitium (in Medieval Latin also servicium) "slavery, condition of a slave, servitude," also "slaves collectively" (in Medieval Latin "service"), from servus "slave" (see serve (v.)).
The meaning "act of serving, occupation of an attendant servant" is attested from c. 1200, as is that of "assistance, help; a helpful act." From c. 1300 as "provision of food; sequence of dishes served in a meal;" from late 14c. as "service at table, attendance during a meal." The sense of "the furniture of the table" (tea service, etc.) is from mid-15c.
Meanings "state of being bound to undertake tasks for someone or at someone's direction" and "labor performed or undertaken for another" are mid-13c. The sense of "service or employment in a court or administration" is from c. 1300, as is that of "military service (especially by a knight); employment as a soldier;" hence "the military as an occupation" (1706).
The meaning "the supplying of electricity, water, gas, etc., for domestic use" is by 1879; later extended to broadcasting (1927), etc. The meaning "expert care or assistance given by manufacturers or dealers to the purchasers of their goods" is by 1919. Service industry (as distinct from production) is attested from 1938; service there indicates the section of the economy that supplies consumer needs but makes no tangible goods (a sense attested by 1936). Service-charge is attested by 1929. A service station originally was a gas stop that also repaired cars.
At your service as a phrase of politeness is attested by c. 1600. Service-book, containing forms for public worship, is attested from 1570s. Also in Middle English, service was "the devotion or suit of a lover" (late 14c.), and "sexual intercourse, conjugal relations" (mid-15c.; service of Venus, or flesh's service).