wi-fi (n.)

1894, in reference to as a type of telegraph, from wire (n.) + -less. As a noun, "radio broadcasting," attested from 1903, subsequently superseded by radio.

1947, abbreviation of high-fidelity (1934), a descriptive term of radio receivers in reference to their quality of sound reproduction. Hi as an advertiser's phonological shortening of high (adj.) is attested by 1914. Fidelity in the sense "faithful reproduction of sound" is from 1878.