"von klein auf" - what "auf" is doing here?

Question

The phrase "von klein auf" supposedly is a fixed phrase meaning "from the early age":

Wir sind schon von klein auf gute Freunde.

My question is, why is "auf" in this phrase? Wouldn't "von klein" make the same sense? If I would leave it out would it be comprehensible?

Small note: Of course I know that fixed phrases are fixed phrases and there is not much to them. But even so, most of the time I understand their grammar and it helps me form other sentences. For example, I know the fixed phrase "Es gibt...". At first I didn't know the grammar because I was taught it as a fixed phrase. But now, I remember conjugation of "geben" thanks to it.

Answer 1

German not only has prepositions but also postpositions. Sometimes both are combined, and often the postposition part is an adverb, or may be understood as a separated prefix of the finite verb.

von klein auf,

"upbrought from little"

von klein an

"starting from little"

von Anfang an, von Beginn an

"starting from the beginning"

von morgen an

"starting from tomorrow"

auf jemanden zu, von jemandem weg

"towards someone to", "from someone away"

vom Ende her, zum Ende hin

"coming from the end", "towards the end to"

Often you can leave out the ending preposition or adverb without changing the meaning. But it affects rhythm, and the alternation of stressed and unstressed syllables is most important in German speech. That's when those tiny bits come in handy.

Answer 2

The preposition von by itself, in its original and still primary meaning, designates a point of origin in the spatial (not temporal) sense. For a temporal point of origin, German has ab and seit.

Ab nächster Woche machen wir Homeoffice.

Ich mache seit heute Homeoffice.

*Ich mache von heute Homeoffice.

However, von can be used as a temporal point of origin if the meaning is supported by another element, for instance bis.

Von heute bis übermorgen mache ich Homeoffice.

Alternatively, an adverb such as an or auf can be added to allow for a temporal interpretation.

Von heute an, ab mache ich Homeoffice.

Maybe von by itself already has too many functions, so that an additional element is required to allow for the temporal interpretation

Answer 3

One might argue that "von ... an" as well as "von ... auf" could be regarded as circumpositions like "um ... willen" or "um ... herum":

Ausnahmsweise widersprach er nicht, um des lieben Friedens willen.

Ich werde so um halb sechs herum zu Hause sein.

There is an idiom meaning the same as von klein auf, that is

von Kindesbeinen an:

Von Kindesbeinen an wurde Nicolas eingeschärft, beim Überqueren der Straße erst nach links und dann nach rechts zu schauen.

For me, the second element of "von ... auf" evokes the idea of 'growing up' = aufwachsen. There is another German idiom giving the same idea, that is

von der Pike auf (= from the bottom up)

evoking the idea of 'sich hocharbeiten' (= working one's way up).

Example:

Obwohl sein Vater Küchenchef im Ritz war, musste er ganz unten anfangen und den Beruf 'von der Pike auf' lernen. Das hieß in seinem Fall, dass seine Karriere als Tellerwäscher begann.

A 'Pike' is a sort of spear, the most simple and cheapest weapon for recruits in the ancient times and in the Middle Ages.