enhance: [14] To enhance something is literally to ‘make it higher’. The word comes via Anglo- Norman enhauncer from Old French enhaucer, a descendant of Vulgar Latin *inaltiāre ‘raise’. This was a verb formed from the Latin intensive prefix in- and the adjective altus ‘high’ (source of English altitude). This original literal sense persisted into English (‘It was a stone, the which was enhanced upright’, William Caxton, Charles the Great 1485), but had largely died out by the end of the 16th century, leaving the field clear for the metaphorical ‘augment’. => altitude
enhance (v.)
late 13c., anhaunsen "to raise, make higher," from Anglo-French enhauncer, probably from Old French enhaucier "make greater, make higher or louder; fatten, foster; raise in esteem," from Vulgar Latin *inaltiare, from Late Latin inaltare "raise, exalt," from altare "make high," from altus "high" (see old). Meaning "raise in station, wealth, or fame" attested in English from c. 1300. Related: Enhanced; enhancing.
The -h- in Old French supposedly is from influence of Frankish *hoh "high." The -n- perhaps is due to association with Provençal enansar, enanzar "promote, further," from enant "before, rather," from Latin in + ante "before."