Dear Gabriel,
> Saddanìti, Suttamàlà, §1144.
Sd 1144 prescribes the primary suffix /ta/ after the verbal root /budh/ in
the formation of the agent-noun /buddha/. Then, according to Sd 1179, /dha/
is substituted for /ta/ and, according to Sd 1216, /d/ is substituted for
the /dh/ of the root /budh/ and this gives us the formation /buddha/ (budh +
ta > budh + dha > bud + dha > buddha).
Best wishes,
Jim