solid: [14] Solid comes via Old French solide from Latin solidus ‘solid, whole’ (source also of English solder and soldier and of the French coin term sou). It went back to the same base (Indo-European *sol-) that produced Latin sollus ‘whole’ (source of English solemn and solicit) and salvus ‘unharmed’ (source of English safe, save, etc). => solder, soldier, solemn, solicit
