Javalinas are actually peccaries - only distantly related to pigs. Feral hogs are domestic pigs that escaped captivity and over generations have reverted to a rather wild, hairy creature - but still a pig.
As it happens ( long story) I have both domestic pigs and a pet javalina. Let me see if I can find a picture of Pshammy. Due to neutering and better nutrition, he is much larger than his wild relatives who are, as you said, medium dog sized.
