Historical linguists are familiar with the concept of doubleting, which comes in two causally distinct types. In the first type, here called “contact-induced doubleting,” borrowing from a related language or dialect gives rise to lexical pairs like English shirt : skirt or wine : vine. In the second type, called “system-internal doubleting,” traces of earlier morphology that have become synchronically opaque distinguish lexical pairs like English grass : graze, glass : glaze, weave : weft, or earlier stress contrasts produce lexical pairs like English one : an. In most cases, the result is a set of two phonologically and semantically similar forms that have the same etymology, but differ in meaning. Austronesian languages contain numerous examples of both contact-induced and system-internal doubleting. The former type closely resembles the phenomenon in other language families, but the latter is strikingly different, as it involves “word-families” with two, three, four, or in some cases more than four variants, nearly all of which appear to be semantically identical. How these variants arose remains a major theoretical challenge.