the word 'sublingual' is a modern scientific term formed by the direct combination of two latin roots. the prefix 'sub-', meaning 'under' or 'below', is a prolific element in english, traceable to the proto-indo-European root upo. the second element, 'lingual', derives from latin 'lingua', meaning 'tongue', which itself evolved from the proto-indo-European root dn̥ǵʰwéh₂s. the compound thus literally means 'under the tongue', a meaning it retains precisely in modern anatomical and medical contexts, such as describing the location of glands or a method of drug administration.

Structure: sub (under) + lingual (tongue) sub- (prefix, from latin 'sub', meaning under, below); lingual (adjective-forming element, from latin 'lingua', meaning tongue, language).