Three of the following four word pairs are alike in a certain way and thus form a group. Which word pair does not belong to that group? (The words must be considered as meaningful English words and must not be grouped based on the number of letters/number of consonants/vowels in the word.)

Four letter-pairs are given below. The letters on the left side of (-) are related to the letters on the right side following a specific logic/rule. Three of them share the same rule. Select the odd one out.

Four letter-pairs are given. The letters on the left side of (-) are related to the letters on the right side of (-) by some logic. Three of them follow the same logic. Select the odd one out.