I spent some time looking through more ancient texts to see if I could find the origin. The earliest I've found so far is 2nd century. Vettius Valens uses the word, αλλοδαπός, translated by Riley as alien. "If malefics are in conjunction with or in opposition to Accomplishment, when this Place is not at an angle, and if they are alien to the nativity and in alien signs and degrees, they then cause destruction of property, even if the Lot of Fortune and its ruler are favorably situated." This is found in the Greek on page 118. The word means alien, foreigner or foreign national.
Ptolemy, from the same era, in his Tetrabiblos, uses alien to describe disjunct signs, stating, "" Disjunct" and" alien" are the names applied to those divisions of the zodiac which have none whatever of the aforesaid familiarities with One another. These are the Ones which belong neither to the class of commanding or obeying, beholding or of equal power, and furthermore they are found to be entirely without share in the four aforesaid aspects, opposition, trine, quartile, and sextile, and are either One or five signs apart; for those which are One sign apart are as it were averted from One another and, though they are two, bound the angle of One, and those that are five signs apart divide the whole circle into unequal parts. while the other aspects make an equal division of the perimeter."
It should be noted that Aries is disjucnt, according to modern definition, to Virgo, yet they behold one another, holding the antiscia degrees, considered of equal power by Ptolemy. Firmicus Maternus taught that signs 2, 6, 8 and 12 distant are alien, those that don't make a major aspect to the ascendant (or sign in question). This is because they can't "see" one another, are passive blind spots or ableptum. Applying this to Leo, Virgo is the 2nd, Capricorn is the 6th, Pisces 8th and Cancer 12th sign from Leo, all considered peregrine if Sun is there, for the most part. The section of Virgo and Capricorn where Sun has dignity is where it is close enough to "see", when there. When at the end of his own sign he can see into the 1st decan of Virgo and also at the very beginning, he can look over his shoulder while opposing Aquarius to see the final face of Capricorn.
I think the idea of a planet being peregrine came from this idea that the sign isn't making a major aspect to the home sign or ascendant, at least during the 2nd century. Yet, the solstice points played a special role, and all the opposites where the contra-antiscia are found. I've had the privilege of giving birth to my Sun contra-antiscion and my 2nd husband is my anti-scion. Yes, friction (18-19Aries Moon-Sun antiscion 11Virgo Sun) but it is completely different than the friction with my 1st husband of 28 years, Aquarius. I guess that makes me the yod in the triad we form.
I suspect this originated in Babylonian astrology.