The middle of a word with six letters is often referred to as the "third" and "fourth" letters, since they occupy the center positions. In a six-letter word, the middle letters can be considered the heart or center of the word. If you're looking for a specific term, "center" is a fitting descriptor, but it is not six letters long.
pigpen
hi
Some six letter words with FF in the middle are:wafflebafflebufferduffermufflepifflesufferduffelpuffindiffer
BROLGA
A chattering bird with six letters
dinghy
carpel
carpel
Its called a pagoda Its called a pagoda
a sample
suitor.
It's called a bridge.