The Spanish word 'lentilla' meaning 'contact lens' comes from the French word 'lentille' with the same meaning. The French term itself derives from the Latin word 'lens', which originally meant 'lentil'. This semantic evolution from 'lentil' to 'contact lens' occurred because early lenses were shaped similar to lentil seeds - having a biconvex shape with curved surfaces on both sides. This connection between the shape of the legume and optical devices has influenced terminology across many languages.

A related Spanish word is 'lente', which means 'lens' or 'eyeglass', and 'lenteja' meaning 'lentil'. Both share the same Latin root 'lens'. This shows how Spanish preserved both the optical and botanical meanings in different but related words.

English speakers will recognize the connection to the word 'lens', which comes directly from the same Latin root. We also have the word 'lentil' for the legume, which shares this etymology. This parallel development shows how both English and Spanish maintained the connection between the shape of the lentil and optical instruments.