The Spanish word 'lengua', meaning both 'tongue' and 'language', comes from the Latin word 'lingua', which had the same dual meaning. 'Lingua' itself evolved from Old Latin 'dingua', meaning 'tongue'. This shows how the physical organ (tongue) became metaphorically associated with the concept of language itself, since the tongue is essential for speech. The change from Old Latin 'd' to Latin 'l' is a known sound change, and the development from Latin 'lingua' to Spanish 'lengua' follows regular sound changes between the two languages.

The word 'lengua' is a fundamental Spanish word and is actually one of the simpler, more basic vocabulary terms that students learn early on. It appears in many derived words like 'lingüística' (linguistics), 'lenguaje' (language), and 'lingüista' (linguist).

English speakers can find familiar connections in words like 'linguistics', 'linguist', and 'multilingual', which all come from the same Latin root 'lingua'. While English uses 'tongue' for the organ in your mouth, we still preserve the 'lingua' root in academic and technical terms relating to language study. The word 'language' itself is also related, though it came through French rather than directly from Latin.