Hello,

Actually by looking a few chapters ahead in the second part of
Buddhadatta (p74) I found the following explanation which kind of
makes sense:

<<A root is a primitive element of the language, expressing an
abstract idea. It is incapable of any grammatical analysis

A. It is common in European languages to express the idea contained in
the root by means of the Infinitive, e.g., Bhuu (to be); but it must
be borne in mind that the root is not an Infinitive, but a primary
element expressing a crude idea.

B. the Classical Pali Grammarians give all roots ending in consonants
with a euphonic vowel at the end, e.g., Pac(a) = to cook; Gam(u)=to
go. This vowel however, does not really belong to the root.>>

With Metta,

Florent