In lambda calculus there are three types of reduction,
$\alpha$-renaming
$\beta$-reduction
$\eta$-conversion
The use of $\eta$ in $\eta$-conversion seems rather strange to me. Since they already used $\alpha$ and $\beta$ I would expect the pattern to be continued with $\gamma$ the third Greek letter, but $\eta$ is used instead.
Why is $\eta$ used in $\eta$-conversion?
