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rel

A unit of magnetic reluctance proposed by Vladimir Karapetoff in 1911, but not adopted.

source

The definition of the unit of reluctance follows directly from eq. (1). A magnetic circuit has a unit reluctance when a magnetomotive force of one ampere-turn produces in it a flux of one maxwell.² No name has been given to this unit so far. The author ventures to suggest the name rel, and he uses it provisionally in this book. Granting that reluctance is a useful quantity in magnetic calculations, one must admit that it should be measured in some units of its own; unless one chooses to use the cumbersome notation “ampere-turns per maxwell.” The name rel is simply the beginning of the word reluctance. Thus, a magnetic circuit has a reluctance of one rel when one ampere-turn produces one maxwell of flux in it. The unit rel is analogous to the ohm in the electric circuit, and to the daraf in the electrostatic circuit.

2. See Appendix I at the end of the book.

V. Karapetoff.
The Magnetic Circuit.
New York: McGraw-Hill Book Company, 1911.
Page 8.