abet
Pronunciation: /əˈbɛt/
verb ( abets, abetting, abetted)

Origin:
late Middle English (in the sense 'urge to do something good or bad'): from Old French abeter, from a- (from Latin ad 'to, at') + beter 'hound, urge on'

Spelling rule
If a verb ends with a single vowel plus a consonant, and the stress is at the end of the word (as in refer), double the last letter when adding -ing or -ed: