Readings & Meanings:
to doubt; suspicion
Once you begin to doubt her, you will start to suspect your wife might be having an affair.
She suspected him of telling lies.
The store manager turned a suspicious look on him, a look that suspected him of shoplifting.
The suspicion that that politician took bribes has all of a sudden just become a huge story.
疋, the main radical, is a pair of legs pointing in opposite directions.
矣's lower part is in the bottom left of 疑. 矣 is a picture of a person coming to a stop and looking behind himself.
The ヒ-looking part on the top left is a form of 子(really?).
The マ on top right is a form of 人 (really).
Okay, so what have we got? A person, whose legs are stuck in an awkward position, because he's looking back at a child.
When you are suspicious, something has captivated your thoughts, and you can't move on from it. You are stuck that way until you can resolve your suspicions.