by the by

by the by

1. used to introduce a new topic; incidentally
   • William Morris

     Well, I lay it down, first, that a book quite unornamented can look actually and positively beautiful, and not merely un-ugly, if it be, so to say, architecturally good, which, by the by, need not add much to its price […]

by the by (comparative more by the by, superlative most by the by)

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   • 1990, Susan Sherman, The color of the heart: writing from struggle & change, 1959-1990:

     These sudden rains. Not tropical - with lightning, thunder, great release after hours of tension. But more nonchalant, more "by-the-by." As if the clouds, rushing to get somewhere else, were to drop some rain in passing.

• by the way