Excel 78 bytes

=TRIM(MID("  disdisil im im ir un",IFERROR(FIND(LEFT(A1),"qhlmpr"),7)*3,3))&A1

I found some close contenders using different methods that scored 81 bytes:

=IFERROR(CHOOSE(FIND(LEFT(A1),"qhlmpr"),"dis","dis","il","im","im","ir"),"un")&A1

And 84 bytes:

=IFERROR(TRIM(MID("im disi"&LEFT(A1),MOD(FIND(LEFT(F1),"qlmhrp"),3)*3+1,3)),"un")&A1