Inchmeal is an adverb that means ‘little by little.’ 

The Old English word meal, in addition to its contemporary use, also meant ‘measure’ or ‘quantity.’ By the mid 16th century, it was combined with the measurement ‘inch’ to describe something happening slowly. Here’s an example:

The worm was crawling inchmeal across the floor. It may take him a while to get there, but he sure seems determined.