ursus.

Undoubtedly from Proto-Indo-European *h₂ŕ̥tḱos (“bear”), though it is not exactly clear how the term developed in Italic. Schrijver postulates an Italic sound-law wherein *#HLC- sequences became aLC- in Latin, as perhaps indicated by terms such as argentum (perhaps from *h₂ŕ̥ǵn̥tom), in which case the initial u- is unexpected. However, the linguist Stefan Höfler argues that *#HLC- operated like other *#CLC- sequences, such as mors (< *mr̥t-), in which case *h₂ŕ̥tḱos would develop into *orksos, whence ursus. Schrijver, however, suggests that—even if *#HLC- yielded Latin #oLC-—the outcome ursus would still be irregular, as the expected result would be **orsus, and it can thus be disregarded as evidence for the ordinary development of *#HLC- in Latin. Another linguist, Frederick Kortlandt, has explained the unusual vocalism as the result of influence from urcō (“to roar”). Ultimately, De Vaan suggests that the unexpected sound changes may have arisen as a taboo distortion. For the outcome -s- from original *-tḱ-, compare sinō. Doublet of Arctos.