Why the atomic orbitals are named as " s(sharp) ,p(principal) ,d (diffused),f(fundamental)?

Scientists began to understand the electron orbitals only
in 1960. Before that there was no clarity about the cause of the spectrums of elements
that scientists were able to identify.

So an attempt was
made to group the patterns of the spectrums. This was done by identifying whether the
lines in the pattern appeared sharp or diffused. Patterns that had the same lines as
that of hydrogen were labeled principal. As scientists began to understand the causes
behind the difference in spectrum lines the names used in spectrums recorded as
photographs were continued as earlier to make things
easier.

This led to the spdf or sharp, principal, diffuse
and fundamental designations.