Linux terminal help

[Adam]

I have a school assignment that I have been stuck on for a couple of days.
What I need is a command that takes a sequence of letters and pairs them in a way that each pair has another adjacent pair next to it.
For example:

abcdefgh

Should give me:

ab cd
bc de
cd ef
de fg
ef gh

I'm familiar with awk, sed and grep, which I think are the tools I'm supposed to use. But I'm still not getting it.