Background:
Israel Gollanz reported the discovery of a fragment of the lost Tale of Wade at the British Philological Society meeting in Feb. 1896^*1, and the Anglo-Saxon quote occurs within a Latin homily dated to early 13th cent.:

{Latin text with Anglo Saxon quote} Triplex enim est humilitas: Humilitas scilicet culpe humilitas pene humilitas enitentie. Hmilitate autem culpe in tantum humilitatus est primus parens noster quod cum dominus tocius mundi efficeretur ante peccatum et in omnibus quae in mundo erant dominaretur post peccatum uero a uili uermiculo scilicet a pulice siue pediculo se minime potuit defendere. Qui similis fuit deo ante peccatum per peccatum factus est dissimilis quia hoc duce rosa numquam uertitur in saliuncam. Adam itaque de homine factus est quasi non homo nec tantum adam sed omnes fere fiunt quasi non homines. Ita quod dicere possunt cum Wade: Summe sende ylves & summe sende nadderes, sumne sende nikeres     the biden watez wunien. Nister man nenne bute     ildebrand onne18. Similiter hodie aliqui sunt lupi utpote potenes tiranni... —text as emended by Wenterdorf*2

{translation} Humility is threefold: humilty of guilt of course, humilty partial[?], humility within. But humility of guilt as such disgraced our first forefather, who was to be created before Sin by the Lord of the whole world, and was to dominiate all the world after Sin; verily a lowly worm as you know can hardly defend itself from flea or lice. The likes of what God made before Sin differs form what he created after Sin, because here, the regal[?] rose never turns into scented nard. Adam made from mankind is as if not a man; not just Adam but almost all were made as unto non-man. In this wise it can be stated, after Wade: "Some are elves, some are adders, and some are nickers that (dwell near the water?). There is no man except Hildebrand alone." Similarly nowadays, some men are wolves in as much as they are mighty tyrants.. —AS trans. Wenterdorf's, Latin tr. mine [except the last sentence which was assimilated with Wenterdorf's translation.]

    I can't vouch for the accuracy of the Latin translation, and I suspect it riddled with errors, for I had quite a bit of trouble with the text, but it is probably not that far off. Wentersdorf's brief summary is:

The passage in which it occurs desls with the Fall of man and the evils resulting from it. Adam, says the preacher, was humbled by wicked­ ness and changed from a man into a kind of non-man, and so were al­ most all other man.

    Anyway, it is sufficient for our purpose, since it does not seem likely that rendering the homily with further precision will shed any more light on the context in which the three AS lines are spoken.

    Wentersdorff makes a meandering and fuzzy attempt to deduce the context in which the fragment occurs.
    There seems to be a more probable solution. This passage might construed as a piece of banter referring to Hildebrand as the only person of pure human stock, surrounded by other heroes of superhuman lineage.

The first line about elves and adders can be paralleled with the contest of insults (ON senna) that takes place between Högni and Thidrek in a version of the Nibelungen saga as preserved in the Þiðrekssaga (Ch. 391 in Haymes' tr.).
    The latter insults Högni for being the son of an elf (he was in fact secretly sired by an elf, ch. 169). Högni retorts by calling his opponent the son of the devil himself. Thidrek, enraged, breathes fire on Högni.

    Although there is an imperfect match here, in that Thidrek is the scion of the devil^*3, in the Faroese Høgna táttur "Ballad of Høgni", tr. Smith Dampier, Tidrik Tattnarson transforms into a venom-spitting dragon.

    The nickers^*4 (that dwell in the water) can easily be identified with Wade himself. For we learn in the Thidrekssaga ch. 57 that Vadi is the son of King Vilkinas and a mermaid (gen. siokononar, i.e., sjá-kona "sea-wife"). It can also refer to his son Weland the Smith, or his grandson Widia (= Wittich, Witega [G.]; Viðga [ON]), the wielder of Mimung. In the German epic Rabenschlacht, Witege is being dangerously pursued by Dietrich when a mermaid kinswoman of his named Wachilde spirits Witege away.