I would hazard a guess at these are "descriptors" that are applied to various passengers depending on situation. They are used for meals, assistance requests and various other things. They are on the printed manifest and are transmitted downline with everything else.
From what I can remember (its been a while!):
The **ML series are meals
If you use a wheelchair you may be assigned WCHR (ok with stairs), WCHS (need to be lifted on), WCHC (need lifting in to seat)
BLND = Blind
DEAF = Deaf
FQTV = Frequent traveller
UMNR = Unaccompanied minor (remember them?)
There are plenty more but they escape me.