Possibly a participle of an unattested verb *mysfelen, from mys- +‎ felen ("to think wrongly; to feel poorly"). By surface analysis, mys- +‎ feling.

mysfeling

1. Foolish, senseless.
   • c. 1382–1395, John Wycliffe , edited by Josiah Forshall and Frederic Madden, The Holy Bible, , volume III, Oxford: At the University Press, published 1850, →OCLC, Ecclesiasticus XVI:20, page 153, column 1:

     And in alle these thingus mys felende, `or unwittie, is the herte, and eche herte is understonden of hym.

     No heart can think upon these things worthily: and who is able to conceive his ways?

   • c. 1382–1395, John Wycliffe , edited by Josiah Forshall and Frederic Madden, The Holy Bible, , volume III, Oxford: At the University Press, published 1850, →OCLC, Ecclesiasticus XXVII:13, page 175, column 1:

     In the myddell of mys felende men kep a wrd to tyme; in the myddel forsothe of men thenkende the lawe of God be thou besi.

     If thou be among the indiscreet, observe the time; but be continually among men of understanding.

mysfeling

1. A foolish person.
   • c. 1382–1395, John Wycliffe , edited by Josiah Forshall and Frederic Madden, The Holy Bible, , volume III, Oxford: At the University Press, published 1850, →OCLC, Ecclesiasticus XXI:21, page 163, column 1:

     As an hous set out of termes, so a wisdam to a fool; and the kunnynge of the mys felende untellable wrdis.

     As is a house that is destroyed, so is wisdom to a fool: and the knowledge of the unwise is as talk without sense.

   • c. 1382–1395, John Wycliffe , edited by Josiah Forshall and Frederic Madden, The Holy Bible, , volume III, Oxford: At the University Press, published 1850, →OCLC, Ecclesiasticus XXII:14-15, page 164, column 1:

     With a fool ne speke thou mych, and with a mys felende go thou not awey. Kep thee fro hym, that thou naue not greef;

     Talk not much with a fool, and go not to him that hath no understanding: beware of him, lest thou have trouble

2. (medicine, hapax legomenon) Numbness.
   • a1475, Platearis Practica brevis fol. 18v, quoted in 2016, Juhani Norri, Dictionary of Medical VOcabulary in English, 1375-1550: Body Parts, Sickness, Instruments, and Medical Preperations; under "misfeeling"

     Ȝyf be in þe sinewis, þan þe stoppynge & mysfyllynge is in þe ouereste partes, as in þe face.

     (please add an English translation of this quotation)

Outside the medical sense, this word is apparently only found in John Wycliffe's translation of Ecclesiasticus, and did not survive into Modern English.