colonel (n.)
1540s, coronell, from Middle French coronel (16c.), modified by dissimilation from Italian colonnella "commander of a column of soldiers at the head of a regiment," from compagna colonella "little column company," from Latin columna "pillar" (see column). English spelling modified 1580s in learned writing to conform with the Italian form (via translations of Italian military manuals), and pronunciations with "r" and "l" coexisted 17c.-18c., but the earlier pronunciation prevailed. Spanish coronel, from Italian, shows a similar evolution by dissimilation.