Historical Linguistics and Language Families 7, Exercise 2: analogy

helped replacing holp: help once had past tense holp and participle holpen.
Other verbs form the past tense with -ed (jumped, carried, defeated). By
analogy, help took -ed, giving helped:

    jump : jumped  ::  help : helped

The source calls this morphological levelling.

dove: American English dove (past of dive) was formed on the pattern of drove
(from drive) and strove (from strive):

    drive : drove  ::  dive : dove

This copies an irregular pattern, so analogy created a form that breaks the
regular -ed rule. Analogy follows a pattern, not necessarily the commonest one.