The OED does not supply any pointers as regards etymology. But this is the entry which provides some interesting examples of its use.
It seems to begin in the late 18th century.
I am thinking that as pertaining to is a very similar expression.
b. as regards, as regarded (now rare), †as regarding: with respect or
1797 Treat. Police Metropolis (ed. 4) iv. 73 A distinction is
made, as regards moral rectitude, in the minds of many individuals.
1824 R. Southey Bk. of Church (1841) 408 That Church, and the
Queen, its refounder, are clear of persecution, as regards the
1848 H. Hallam Suppl. Notes View Europe Middle Ages ii. 78
Especially as regards the Visigothic and Burgundian partitions.
1884 R. Browning Ferishtah's Fancies 111, I am in motion, and all
things beside That circle round my passage through their
midst,—Motionless, these are, as regarding me.
1885 Law Times Rep. 52 651/1 He was in a thoroughly sound
condition as regards intellect.
1920 R. Macaulay Potterism i. i. 5 He was one up on her as regards
life, owing to that awful business sex.
1937 Times 16 Apr. 23/6 And this in spite of the fact that they
were especially unfortunate as regarded the weather during the holiday
1976 J. Lukasiewicz Railway Game 120 As regards the maximum rates,
these are prescribed when there is no competitive mode of transport.
2005 M. Roach Spook 13 For millions of people, religion will turn
out to have been a bum steer as regards the hereafter.