Similar words in different languages can be similar for four primary reasons: (i) the similarity is due to chance, (ii) the languages are genetically related, (iii) the form is borrowed, either from one language to the other or both from the same external source, or (iv) the words are similar due to some language universal. If languages are unrelated and in contact, the most likely scenario is usually (iii). Some examples are included below.
|Language||Family||Word for 'cat'||Source|
|Munsee Delaware||Algonquian||póóšiiš||Swiggers (1985)|
|Blackfoot||Algonquian||póós||Frantz & Russell (1995)|
|Chinook Jargon||Chinookan||pús(h)||James Crippen (p.c.)|
|Umatilla Sahaptin||Sahaptian||p'uus||Thomas Morningowl (p.c.)|
|Walla Walla Sahaptin||Sahaptian||p'uus, pišpiš||Thomas Morningowl (p.c.)|
|Nez Perce||Sahaptian||pic||Aoki (1994)|
|Cayuse||isolate||picpic||Thomas Morningowl (p.c.)|
|Tlingit||Na-Dene||dóosh||James Crippen (p.c.)|
|Coast Tsimshian||Tsimshianic||dúus||Dunn (1979)|
Most likely these forms are from a combination of diffused borrowings from Dutch poes, the vocative form for 'cat' (i.e., how Dutch people address(ed) cats), English 'puss' and the English vocative 'psspss' used to call a cat. This would explain the prevalence of three types of forms: those that approximate poos, those that approximate pus (including almost all of the Salishan language, which I haven't included above), and those that approximate pispis. One piece of evidence that these are diffused borrowings rather than individual ones is that while Tlingit lacks labials, and thus has a form beginning with /d/ instead of /p/, Tsimshian and Haida have /p/, and thus must have borrowed the form from Tlingit rather than English or Dutch. James Crippen notes that the Tlingit form in turn is a borrowing from Chinook Jargon.
It's not clear what's so special about the word 'cat', but many northern languages have almost identical forms for this word, while other animal names are quite different. For example, the word for 'chicken' in the same languages displays remarkable variation, ranging from English borrowings to French borrowings to onomatopoetic terms to descriptive neologisms. Besides the northern languages, southeastern and southwestern languages also have very similar terms for 'cat', though they are from different borrowings (often old Spanish mozo or English 'kitty').