If I search for the string "aa" (no quotes) matches are returned that only contain a single a. I'm running search in texis with these settings: <apicp qminwordlen 1> <apicp minwordlen 1> <apicp keepnoise 1>
In addition to suffixes in the suffix list, with suffixproc on (the default), a trailing vowel is also removed/ignored in searches, so that e.g. `daisies' will match `daisy'. Thus with minwordlen 1, `aa' can be reduced to `a' and matches it.