From Webster's Revised Unabridged Dictionary (1913) [web1913]:

    So-called \So"-called`\, a.
       So named; called by such a name (but perhaps called thus with
       doubtful propriety).

  From WordNet (r) 2.0 [wn]:

    so-called
         adj : doubtful or suspect; "these so-called experts are no help"
               [syn: {alleged(a)}, {supposed}]

My strong conviction is that widespread use of 'so gennant'
or 'sogennant' in German has led to the creeping misuse of
'so-called' in English (especially through technical writings).

In English, it would be better to use:

  what is called

or a better translation of 'so gennant':

  so named
Signed-off-by: NMichael Witten <mfwitten@gmail.com>