The Collaborative International Dictionary of English v.0.48:

Stem \Stem\, v. t. [imp. & p. p. Stemmed; p. pr. & vb. n.
   Stemming.] [Either from stem, n., or akin to stammer; cf.
   G. stemmen to press against.]
   To oppose or cut with, or as with, the stem of a vessel; to
   resist, or make progress against; to stop or check the flow
   of, as a current. "An argosy to stem the waves." --Shak.
   [1913 Webster]

         [They] stem the flood with their erected breasts.
                                                  --Denham.
   [1913 Webster]

         Stemmed the wild torrent of a barbarous age. --Pope.
   [1913 Webster]

The Free On-line Dictionary of Computing (30 December 2018):

stemmer
stemming

    A program or algorithm
   which determines the morphological root of a given inflected
   (or, sometimes, derived) word form -- generally a written word
   form.

   A stemmer for English, for example, should identify the
   string "cats" (and possibly "catlike", "catty" etc.) as
   based on the root "cat", and "stemmer", "stemming", "stemmed"
   as based on "stem".

   English stemmers are fairly trivial (with only occasional
   problems, such as "dries" being the third-person singular
   present form of the verb "dry", "axes" being the plural of
   "ax" as well as "axis"); but stemmers become harder to design
   as the morphology, orthography, and character encoding of
   the target language becomes more complex.  For example, an
   Italian stemmer is more complex than an English one (because
   of more possible verb inflections), a Russian one is more
   complex (more possible noun declensions), a Hebrew one is even
   more complex (a hairy writing system), and so on.

   Stemmers are common elements in query systems, since a user
   who runs a query on "daffodils" probably cares about documents
   that contain the word "daffodil" (without the s).

   (This dictionary has a rudimentary stemmer which currently
   (April 1997) handles only conversion of plurals to singulars).

   (1997-04-09)