For a short period in medical history hyleg was a polite way of referring to what was thought to be a form of painless gout localized in the hams rather than in the extremities. It was considered to be an extreme concentration of phlegm caused by an afflicted Jupiter in Sagittarius. Nowadays, no longer a medical condition, it is considered a nuisance, particularily with the feminine population. But this is not hyleg. There must have been a misunderstanding of the Persian, which is itself a translation of the Greek word aphetes, which is the significator of life in a natal chart.
Now and then you will find astrologers signing their letters with “aphetically” yours but they were just writing sloppily and really meant “affectionately yours”…