early 15c., tonel, "funnel-shaped net for catching birds," from Old French tonnelle "net," or tonel "cask," diminutive of Old French tonne "tun, cask for liquids," possibly from the same source as Old English tunne (see tun).
Sense of "tube, pipe" (1540s) developed in English and led to sense of "underground passage" (1660s). This sense subsequently has been borrowed into French (1878). The earlier native word for this was mine (n.). Meaning "burrow of an animal" is from 1873. Tunnel vision is attested from 1912. The amusement park tunnel of love is attested from 1911 (in reference to New York's Luna Park). The figurative light at the end of the tunnel has been seen since 1882.
The "Tunnel of Love," an attraction found at many amusement parks, has been responsible for a surprising number of proposals. In this and similar devices, couples are allowed to drift through dark or semi-dark underground caverns, usually in a boat or gondola borne on an artificial stream of water. ... Their dim interiors often give a bashful young man the opportunity to propose. [The American Magazine, July 1922]