In this answer, simplification is stated as one reason for spelling variations in American English. But unlike in color and favorite, the number of letters to spell the word in fulfil increases in American English.
Other than for “creating a distinct” variant, is there any reason for the change? Going by the etymology the ideal spelling should be fullfill, so even that may be not a motivation.
Interesting question 🙂 Reading up on this has been a pretty crazy experience. My conclusions are the following:
- The reason for the change from fulfil to fulfill is attributed to inflection, with the spelling modified to suit the function of the word.
- The reason why it isn’t spelt fullfill is similar to why parallel only retains the single ‘l’ at the end—to curb the apparent fugliness of an ‘-llell’ cluster in words such as unparalleled etc.
- There is also a question of consistency involved.
But, unfortunately, another rule in the AE transition was to preserve the “base” word as much as possible, which is why skill/_skilful in BE became skill/skillful in AE. However, this introduced a cluster of letters in words such as skillfully. To put it mildly, the result of exercise was and remains consistently inconsistent.
A related question on the difference in the AE/BE spellings of propelling covers similar territory. It also points to a WP page detailing the differences between American and British spelling which includes the following section on the madness of doubled consonants:
- The word parallel keeps a single -l- in British English, as in American English (paralleling, unparalleled), to avoid the unappealing
- Words with two vowels before a final l are also spelled with -ll- in British English before a suffix when the first vowel either acts as
a consonant (equalling and initialled; in the United States, equaling
or initialed), or belongs to a separate syllable (British fu•el•ling
and di•alled; American fu•el•ing and di•aled).
- British woollen is a further exception due to the double vowel (American: woolen). Also, wooly is accepted in American English,
though woolly prevails in both systems.
There’s also a note on -ful and -fil:
In both American and British usages, words normally spelled -ll
usually drop the second l when used as prefixes or suffixes, for
example full→useful, handful; all→almighty, altogether; well→welfare,
welcome; chill→chilblain. The British fulfil and American fulfill are
never fullfill or fullfil. Johnson wavered on this issue. His
dictionary of 1755 lemmatises distil and instill, downhil and uphill.