You might find it worth while to get a grammar book, or something like the Collins "Easy Learning Irish Verbs". Irish verbs are grouped into two categories ("conjugations") which are divided between those that form their present tense with (e)ann (first conjugation) and those that use (a)íonn (second conjugation). Most first conjugation verbs have a base form ("root") of one syllable, like ith (eat) or fan (wait) which give itheann and fanann respectively. Some first conjugation verbs have a root of more than one syllable. You just have to learn those. All second conjugation verbs have a root of two or more syllables, like dúisigh (waken) or codail (sleep) which yield dúisíonn and codlaíonn respectively. As you may already know, the bracketed (a) and (e) in both categories is a spelling "fix" to match with the broad or slender vowel in the preceding syllable.
This is an English language issue. "Fetch" is a synonym for "collect". See #3 example in Concise Oxford Thesaurus https://en.oxforddictionaries.com/thesaurus/collect