Etymology

The sense of this compound is probably best accounted for by some ON input: (1) Formally, the first element could be explained simply by OE stæf 'staff, stick, rod' (obscurely related by TGD; Kullnick (10) derives the ME directly from an unattested OE stæf-full), but the sense development would be hard to account for. (2) A Norw compound stappfull 'crammed full' offers a much closer parallel to the sense. It is formed on the v. recorded in OIcel as stappa 'to stamp, stamp down; dray in a mortar', probably continuing PGmc *stampan- with OWN assimilation (cp. ME stampen (PDE stamp), WFris, MLG, MDu stampe, OHG stamfōn). Loan into English of an ON compound like the Norw one would entail further assimilation of /pf/ > /ff/, a development which plausibly could have occurred due to association with OE stæf. 

PGmc Ancestor

(1) *staƀ-az; (2) *stamp-

Proposed ON Etymon (OIcel representative)

(2) stappa (v.) 'to stamp, stamp down; dray in a mortar'
(ONP (2) stappa (2) (vb.))

Other Scandinavian Reflexes

(2) Norw stappfull; cp. Far stappa, Icel stappa, Norw stappa, ODan stappe

OE Cognate

(1)  stæf 'staff, stick, rod' 

Phonological and morphological markers

[ON consonant cluster assimilation] (may not be applicable)

Summary category

D1c

Attestation

There is an evident dial bias in MED's five citations, of which the earliest comes from Gaw, two come from WA and one from the Chs. text a1475 Liber Cocorum (Sln 1986).

Occurrences in the Gersum Corpus

Gaw 494; WA 1543, 4897

Bibliography

MED staf-ful (adj.) , OED staff-full (adj.) , HTOED , Dance staf-ful; (1) OED staff (n.1) , MED staf (n.) , Orel *staƀiz ~ *staƀaz, Kroonen *staba-, AEW stæf; (2) de Vries stappa (2), Mag. stappa, Torp NnEO stappa, Seebold stap-ja- (stamp-), Orel *stampōjanan, Kroonen *stamp/bōn-, OED stamp v.