The Greek πρασιαὶ πρασιαὶ (prasiai prasiai) that is typically not directly translated in English (the UBS Handbook says: prasia (only here in the N.T.) meant originally ‘a garden plot’; when used as here it means ‘in orderly groups,’ ‘in rows,’ ‘in ranks’) is translated as “looking like flower beds set side to side” by Pakaluk (2019) (the complete verse: And they sat down in groups of a hundred and groups of fifty, looking like flower beds set side to side).
Palaluk explains (p. 108f.): “These are fascinating lines [verses 39 and 40]. Mark uses two idioms that occur only here in recorded Greek literature: “dinner parties, side by side” and “looking like flower beds set side to side.” The phrase for the first is sumposia sumposia. A symposium is literally a drinking party, though we would say dinner party. The phrase for the second is prasiai prasiai. A prasia is a flower bed. Mark repeats each word so that the position of the words in the sentence, side by side, is like the position of the things represented by the words, side by side. It is very clever. But notice this. Jesus commands the disciples to seat everyone in groups like dinner parties. But in following the command, the disciples seat everyone in groups of fifty or one hundred, in rectangular formations. The first sentence records the Lord’s command; the second is Peter’s [Mark’s assumed source for the gospel] vivid description of how it looked after the fact. The contrast between the two expressions shows that Jesus would leave the details to the disciples’ discretion as they followed his command. The apostles are given scope to set down definite realizations of what the Lord intends.”
Wuest (1961) and Blakwelder (1980) offer similar translations. While Ruden (2021) does not, she explains in a footnote (p. 23): “To depict this unconventional feast, outdoor terms are whimsically combined with terms for an ordinary indoor social gathering. The arrangement of the diners here is literally ‘drinking parties drinking parties,’ ‘on the green greenery,’ and ‘garden plots garden plots.’ Two are expressions like the modern Greek plai plai for ‘side by side.'”
