The Spanish word 'percebe' (meaning 'barnacle') comes from Latin 'pollicipes', which was a compound word literally meaning 'thumb-foot'. This Latin term was formed by combining 'pollex' (meaning 'thumb') and 'pes' (meaning 'foot'). The word entered Spanish through Galician 'percebe', maintaining the same meaning.

The name 'thumb-foot' was likely given to these crustaceans because of their appearance - they have a fleshy stalk that somewhat resembles a thumb or toe, with a shell-covered head at the end, giving them a foot-like appearance.

While 'percebe' itself doesn't have many common Spanish relatives, it's worth noting that the Latin root 'pes' (foot) appears in many Spanish words like 'pie' (foot), 'pedal' (pedal), and 'peatón' (pedestrian).

English speakers might recognize the Latin roots in words like 'pedal', 'pedestrian', and 'pedicure', which all come from the Latin 'pes' (foot). The 'pollex' part of the original Latin word survives in the anatomical term 'pollex', which refers to the thumb in medical contexts.