A seventh of three hundred and sixty degrees is fifty one degrees, twenty five minutes and about forty three seconds, and it never resolves into a whole number. That single fact governs everything about the septile. It cannot be found by counting signs, because seven does not divide twelve. It cannot be drawn on a traditional chart wheel, which is built from twelves. It can only be measured, and only once measurement is precise enough to be worth doing.
This is why the septile has no classical history. It appears in the modern period among writers extending Kepler's harmonic argument, and it belongs entirely to the school that treats an aspect as a division of the circle rather than as a relation between signs. Even within that school it is treated as marginal, and the orb given to it is very tight, often under a degree, since a wider one would run into the semi-square on one side and the sextile on the other.
The interpretations attached to it lean on the symbolism of seven rather than on any observational record: compulsion, fatedness, the irrational, the sense of being carried by something not chosen. Those readings should be identified as what they are, an argument from number symbolism, because there is no body of traditional testimony behind them to appeal to. The septile is best described as a genuine geometric division of the circle whose astrological meaning is asserted rather than inherited, and a reader is entitled to know that before it is used to explain anything.