"hybrid of a tangerine and a pomelo," 1904, the word formed like the fruit.
Entries linking to tangelo
tangerine n.
1842, from tangerine orange (1820) "an orange from Tangier," seaport in northern Morocco, from which it was imported to Britain originally. As an adjective meaning "from Tangier," attested from 1710, probably from Spanish tangerino. As a color name, attested from 1899.
pomelo n.
"grapefruit-like fruit," 1858, of uncertain origin; apparently related to Latin pomum "fruit; apple" (see Pomona).