Etymologically, this may be less than certain. German Stiftung ("foundation"), stiften ("to found, donate") or simply Stift as in Altenstift ("pension home") might derive from this, but that's uncertain.

Since all houses would be build like this ("Pfahlbauten") on marsh land, only foreign visitors would find it an outstanding feature. It's conceivable that this would be noted in official books, but the setting is an opportunity for misunderstandings (case in point, marsh may or may not refer to outskirts, borderland, wasteland, but I mean swamps).

Stift ("peg") has otherwise come to mean "pen, pencil" (initially of charcoal, I believe), but there is no related verb that I'm aware of (ie. no to pen, to sign). Another sense, "apprentice" (also Stippie, Stepke, potentially "child"), might be like an intern of the foundation, but stepchild offers another possibility if the intern was an orphan and the church took them in (see also staff).

It's notable that the steps of a ladder are little more than pegs, although step and step- are held distinct,

through Proto-Indo-European roots (wiktionary):

* stebʰ- ("to stand still, to harden")

* steyp- ("stiff, errect")

* stab- (“to support, stomp, curse, be amazed”)

* (s)tewp- (“to push, strike”)

are supposed to derive

staff / stave (G Stab)

stiff (thus G Stift beside steif "stiff")

step (G Stufe, stapfen only in Fussstapfen "foot prints, etc.)

step-* (G stief-), "Related to Old English stīepan (“to deprive, bereave”)

This is rather inscrutable because small details like a vowel can be found incompatible with a reconstruction, indicating eg. a loanword, but phonology alone is not enough. The final consonants -p or -b may be conditioned by vowel length and the development of the auslaut through Kluge's law is uncertain anyway. There is a virtually endless plethora of such words in st- (stage, stand, stick, stuck, sturdy, ...).

So, nobody can really say that they are not related, and the dating may be questionable. The modus operandi is to separate them until proof to the opposite. Albeit, the reconstruction depends on the choice of comparanda and a good theory to explain them. A theory is only as good as the explanations that it has to offer. Or in other words, there is a big difference between working within a framework, rather mechanically, or trying to set-up, extend and complete the frame. Now PIE stab-, steb- or stebʰ- are alternative reconstructions, the former from overcome theories with less precise phonology. However, historical linguistics is intimately related to, well, history and the evidence that they can afford. Relative chronologies as for the spread of Christendom depend on so many factors and technology, more recently, that it is very difficult to date something not before. Textual evidence only allows at the latest, as a rule.

Nevertheless, I have a hunch that stub* may be related (PIE (s)tew-, "compare steep* (“sharp slope”)"). I never thought of a stub-article as a foundation, perhaps because it may get shaved for various reasons. G Stoppel ("stubble") on the other hand is from Latin stipula, through Low German, from PIE steyp-. I thought for a moment that the typographic sense of stub ("A row heading in a table [...]") equates to G Staffel- ("table"), staffeln (to cascade; NB: cp. scada "ladder"), etc. Stipulation (boilerplate) doesn't work any better. The stuff of legends (G Stoff) is interesting, given the legend on a map. Be that as it may, little churches had probably started as outposts, bridge-heads in a sense.

There is also Serbo-Croatian snub "pillar", a regular cognate of Polish kościół słupowy ("stave church")! The connotation does not speak well of the church, indicating corruption, see słop: shell corporation, straw owner.