"mixed ale"?

[Jesse Sheidlower]

Is anyone familiar with the term "mixed ale"? We have a small number of
examples from the 1880s to the 1930s (the last from the Tamony Collection),
mostly in figurative uses apparently meaning 'poor', and apparently in
reference to the result of drinking mixed ale.

It is not clear, though, what the ale is mixed with. The earliest quote
we have is from the 1886 edition of Webster's and reads:

_Slape-ale_, plain ale, as opposed to medicated or *mixed ale.

Any input would be appreciated.

Thanks,

Jesse Sheidlower
OED