There is a sound in English called a GLOTTAL CATCH or GLOTTAL STOP, which is a stop consonant articulated without release and having glottal occlusion as a secondary articulation, as in the Scottish articulation of the sound t of little, bottle, etc. This sound is present in nearly all dialects of English as an allophone of /t/ in syllable codas and is symbolized orthographically as an apostrophe, e. g., sto’p, tha’t, kno’ck, wa’tch, lea’p, soa’k, hel’p, pin’ch, etc. It also occurs in word-final position, where it is represented with a p, as in yep for yes and nope for no. To generalize, the incidence of a glottal catch at the end of a syllable is a kind of APOCOPE, i. e., a truncation.
It is also a PHONOSTYLISTIC datum, in that it is characteristic of informal speech and is not normative of neutral or formal style. In this respect, as a species of truncation (of the syllable), it fits into the general pattern whereby informality is achieved via ABBREVIATION vis-à-vis its formal counterpart.
One aspect of informal or colloquial style is the AFFECTIVE meaning of abbreviation, specifically its close association with the phenomenon known as HYPOCORISM (as in baby talk). This form of endearment is typical, for instance, of pet names, wherein abbreviated versions of their full neutral or formal counterparts are the norm.
In this light it becomes clear why the word football is commonly heard uttered by ardent fans and followers of the sport with a glottal catch for the t ending the first constituent of this compound, whatever the stylistic context or the utterer’s dialectal profile. In such speakers’ value system football is a hypocoristic, hence to be pronounced uniformly––regardless of context––with a phonetic feature answering to a term of endearment.