Now, the -t being considered as part of the root, the -s cannot be derived from the second singular; inasmuch as it precedes, instead of following the -t.
At one time, for want of a better theory, I conceived, that in the word in point (and also in durst and a few others), we had traces of the Scandinavian passive. This notion I have, for evident reasons, abandoned.
In p. [298] it was stated that the Mœso-Gothic termination of the second singular of the strong præterites was -t. It is
here mentioned that must is a præterite form. Now the final letter of the root mot, and the sign of the second singular of the strong præterite, are the same, -t. Now, as -t cannot be immediately added to t, the natural form of the second singular mót-t is impracticable. Hence, before the -t of the second person, the -t of the root is changed, so that, instead of máimáit-t, bigat-t, fáifalþ-t, láilot-t, &c., we have máimáis-t, bigas-t, fáifals-t, láilos-t, &c., Mœso-Gothic.—See Deutsche Grammatik, 844.
The euphonic reason for the -s, in must, is sufficient to show that it is in a different predicament from durst.
The provincial form mun, there or thereabouts equivalent in meaning to must, has no etymological connexion with this last named word. It is a distinct word, in Scandinavian monne.
Wist.—In its present form a regular præterite from wiss=know. The difficulties of this word arise from the parallel forms wit (as in to wit), and wot=knew. The following are the forms of this peculiar word:—
In Mœso-Gothic, 1 sing. pres. ind. váit; 2. do., váist; 1. pl. vitum; præterite 1. s. vissa; 2 vissêss; 1. pl. vissêdum. From the form váist we see that the second singular is formed after the manner of must; that is, váist stands instead of váit-t. From the form vissêdum we see that the præterite is not strong, but weak; therefore that vissa is euphonic for vista.
In Anglo-Saxon.—Wât, wâst, witon, wiste and wisse, wiston.—Here the double forms, wiste and wisse, verify the statement concerning the Mœso-Gothic vissa.
In Icelandic.—Veit, veizt, vitum, vissi. Danish ved, vide, vidste. Observe the form vidste; since, in it, the -d of the root (in spelling, at least), is preserved. The -t of the Anglo-Saxon wiste is the -t, not of the root, but of the inflection.