clipping of "almost all"
very nearly but not exactly or entirely (99% of all)
"Almost all" can sometimes
diminish the majesty of the subject. This is
truer when the "almost" is supposed to depict 99.99% of "all".
Hence comes the need for this word. "Alll" looks and sounds very similar to "all", hence it feels like the progress is very very close to "all".
In spoken English, the word is pronounced similar to "all" but the last "l" is pronounce with a sharp sound.