Exegesis:

ēgnooun (only here in Mark) ‘they did not know,’ ‘they were ignorant (about)’: in this context, ‘they did not understand.’

to rēma (14.72) ‘word,’ ‘saying,’ ‘expression,’ with the special meaning in this context of ‘prophecy,’ ‘prediction.’

ephobounto auton eperōtēsai ‘they were afraid to ask him’: the infinitive epērōtēsai ‘to ask’ completes the meaning of the main verb ephobounto ‘they were afraid,’ while auton ‘him’ is the direct object of the infinitive.

Translation:

It is rarely that one can find a noun expression equivalent to the Greek rēma or English saying. Usually, the only corresponding expression is ‘what he was saying’ or ‘what he meant when he was saying,’ for the men were not ignorant of the words which Jesus used, but of the implications of what he was trying to communicate to them.

To ask him may require expansion in some languages by the addition of the direct object (or second object, as it is sometimes called), e.g. ‘to ask him what he meant’ or ‘to ask him what his words meant.’

Quoted with permission from Bratcher, Robert G. and Nida, Eugene A. A Handbook on the Gospel of Mark. (UBS Handbook Series). New York: UBS, 1961. For this and other handbooks for translators see here .