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-al (2), -ar (1) Adjective-forming suffix.
From Latin -alis 'id.' and -aris 'id.' respectively. From Proto-Italic *-li- 'id.' and *-ri- 'id.' From Proto-Indo-European *-li̯- 'id.'

If Proto-Indo-European had a single affix *-li̯-, then how did Proto-Italic end up with both *-li- and *-ri-? The answer is that in Proto-Italic the old suffix was *-li-, which changed to *-ri- in the word *keli-ri-s "fast" due to dissimilation (see célere). Thus, a new suffix was born.