Verbs with vowel shortening and devoicing of the ending
Many verbs derive from Germanic strong verbs, which make many of their inflected forms through vowel gradation, as can be observed in Modern English patterns.
Some of the verbs in this and in the preceding group have alternative regular forms, such as DREAMED and LEAPED.
To find the correct form, you can use an online database of the irregular verbs.
For example: irregular verb DREAM