I know that there exist some verbs which were formed in Proto-Germanic by adding the causative marker -ja- to nouns or adjectives, such as these pairs:
- doom (noun) > deem (verb)
- food (noun) > feed (verb)
- tale (noun) > tell (verb)
- full (adj) > fill (verb)
- blood (noun) > bleed (verb)
- hale (adj) > heal (verb)
However, I'm not too sure about how those evolved from the original word until now. I supposed it is related to I/J-Mutation. http://www.etymonline.com/imutate.php
Could you please explain it properly?