Simple past - Wikipedia
https://en.wikipedia.org/wiki/Simple_pastRegular verbs form the simple past end-ed; however there are a few hundred irregular verbs with different forms. The spelling rules for forming the past simple of regular verbs are as follows: verbs ending in -e add only –d to the end (e.g. live – lived, not *liveed), verbs ending in -y change to -ied (e.g. study – studied) and verbs ending in a group of a consonant + a vowel + a consonant double the final consonant (e.g. stop – stopped). For details see English verbs § Past tense.