The English language is rather strange. There are many words that follow a common rule and many that do not. English is a fusion of Anglican dialects and other influences such as Latin, French, Spanish and German, but that doesn't mean an occasional Russian word doesn't find its way into the lexicon. As language is organic and changing daily, dictionaries are often updated to reflect present-day slang such as the word "dis" meaning to treat with disrespect. With all these complications some words really stick out as conundrums, like the world 'colonel.' So, why is 'colonel' pronounced 'kernel,' as in kernel of corn?
Colonel's roots in Roman architecture
Just as war has been around for ages, terms of war have been around. Just as war has entailed pillaging and taking, encountered words have been copped and mined from the lands pillaged. The world 'colonel' has a Latin root, as so many words do. According to the Dictionary.com, the world columna means 'pillar,' or 'column'-and there were many columns in ancient Rome. Columns were crucial to the development of high-level structures and high-level civilization. As all roads led to Rome, they also led out of Rome. Roman roads spidered off to distant lands to be conquered. The roads reached out as far north as Great Britain, where the word 'colonel' became the spoila optima, or rich spoils, of the conquered, traveling from Rome to Italy, then France and England.
Latin to Italian
Many English words have come from a Latin origin, and not simply due to the conquering Romans. The church and European intellectual life relied heavily upon Latin-the civilized, proper language-as opposed to regional dialects thought to be barbaric tongues of backward tribes that wouldn't survive standardization. The Latin columna, became the Italian colonnello from campagna colonnella, meaning 'little column company,' a military reference. Colonnello came to mean a commander of a column of soldiers at the head of a regiment. Presumably, a column of soldiers was dubbed so because of the appearance made by the large groups of soldiers in linear formation and their resemblance to powerful columns or pillars of men.
The French iteration, Anglicization and modern usage
As the term moved westward, the French adopted it, too. Colonnello became coronel as of the 16th century, around 1540. Then, as the word was used and spelled in English, the choice was to go back to Italian origins, as research in Italian military manuals led linguistic scholars to this "proper" spelling-colonel. However, the pronunciation in 1580 allowed for both the 'r' and 'l' sounds. The two pronunciations continued until around the 18th century, when the French pronunciation prevailed, leading 'colonel' to be commonly pronounced as 'coronel,' or 'kernel,' as the word is pronounced today. According to Dictionary.com, the word 'colonel' today refers to 'an officer in the U.S. Army, Air force, or Marine Corps ranking between lieutenant colonel and brigadier general: corresponding to a captain in the U.S. Navy.'