The "Z" prefix (omitted in 1973) was used from January to June 1985.

After ZZZ-999, several letter groups ("words") were used.
These combinations were originally omitted from the 1973-84 general issue,
but I guess at this point they were deemed "OK" for use.

They were primarily issued during late June, July, August, and September of 1985.

Here are a few of the ones we know (or suspect) were in this group:
ALE ● BAG ● BAT ● BOX ● BRP ● BUB ● CAN ● CON ● COW ● EGO● END
FEM ● FEY ● FIB ● FLU ● FOD ● FOE ● FOG ● FRT ● GAB ● GUI
HEC ● HEN ● HIP ● HMO ● IDO ● IHS ● IJU ● ILL ● IMP ● INK ● INU ● IVD
JAZ ● JIP ● JUG ● KAT ● KIC ● KOW ● RAG ● RAW ● RED ● RUT ● RYE
HEY (prefix)

Without actual registration documents, it's impossible to tell with 100% certainty which are "word plates" and which are not.
This data is a best guess.

There may have been other plates issued over the years with unused prefixes.
I have a report of the LOW and VEK suffixes being issued to vehicles in 1987 (from Steve Bier).

The new series started at AAA-10A in August 1985 after the "word" plates were exhausted.

This series stopped in November 1992 at HZZ-99Z.