(dialectal or archaic) To slip or slide, especially clumsily, or in a gingerly, timorous way.
He sliddered down as best as he could.
Origin of slidder
From Middle English slyderen, slidren, from Old English sliderian (“to slip”), from Proto-Germanic*slidrōną (“to slide”), from Proto-Indo-European*sleidh- (“to slip”). Cognate with Middle Dutch slideren (“to drag, train”), Germanschlittern (“to slip, slide”).
From Middle English slider, from Old English slidor (“slippery”), from Proto-Germanic*slidaraz, *slidraz (“slippery”), from Proto-Indo-European*sleidh- (“to slip, glide”). Related to Old English slīdan (“to slide”). More at slide.