"SA" refers to the Silmarillion Appendix. A reference like
"SA:aglar" means that the Quenya word (in this case alcar,
alkar) is found under the entry aglar in this Appendix.
When the Quenya word is itself the head of the entry, the reference
is simply "SA". From this Appendix it is not always clear which words
are Quenya, which are primitive forms and which are Sindarin; in such
cases, the Quenya words are identified by means of other sources or
(with less certainty) by their style.