I thought this was an interesting development: one of the common names of the bladder campion in Catalan seems to come from Latin cauliculum "little cabbage". However, instead of the expected development **colill, which you actually find in the standard language is colís and colitx.
These both have their roots in dialect forms. Catalan has a dialectal form of iotization affecting the Vulgar Latin medial clusters c'l, g'l, t'l, and ly (from prevocalic li and le). In Standard Catalan, these all yield /ʎ/, written ll. But in Balearic Catalan and an area of northeast Catalonia roughly coterminous with the Province of Girona, the outcome is /j/, which disappears next to /i/. So, for instance:
lentīcula > VL. lentīc'la > Standard lentilla, dial. llentia[*]
cauliculum > *colic'lu > /coˈlij/ > /cuˈli/.
The form colís is etymologically plural, but because it wasn't recognised as such (since -í is rare in native words but -ís is a relatively common suffix), it was reanalysed as a singular and a new analogical plural colissos was created. (The name of the plant most often occurs in the plural.)
A similar thing happened to colitx, which derives from a dialectal plural form found in the speech of Tarragona. Here /ʎs/ was affricated to [ʧ] and fell together with /ʧ/ from other sources (mostly borrowings from Spanish and Italian). Once again, it was taken for a singular form and the new plural colitxos derived from it.
In other varieties, yet another type of reanalysis happened: The medial /l/ was dissimilated to /n/ under the influence of existing conill "rabbit". (The flowers, though small, are white and fluffy, reminiscent of rabbit fur.) So now in contemporary Catalan, the forms colissos, colitxos, and conills are all current (alone with a couple dozen other variants).
[*] Note that there is a parallel development in Castilian whereby these same clusters yielded Old Spanish /ʒ/ in contrast to the /ʎ/ arising from ll. So lentīcula > VL. lentic'la > OSp. lenteja vs punctillum > puntillo.
"Richmond is a real scholar; Owen just learns languages because he can't bear not to know what other people are saying."--Margaret Lattimore on her two sons