To help illustrate some of the excellent posts above, I've made a quick-and-dirty estimate of how often you might expect to find such seemingly common phrases in an Electrum seed. Intuitively, it may seem that it should only happen rarely if the seed is truly random, but in fact it's not all that uncommon.
I downloaded the
1,000,000 most common 2-grams (phrases of 2 words) from
BYU's
Corpus of Contemporary American English. There were 61,721 common 2-grams on this list where both words were from Electrum's list of 1,626 possible seed words. So:
Let w be the count of
all possible 2-grams of words taken from Electrum's word list.
w = 1626
2Out of these w possible permutations, 61,721 are on the downloaded list of common 2-grams.
Let S be the event where a
single pair of randomly chosen words is in the common list.
P(S) = 61721 / w ≈ 2.3% (probability a single random pair
is common)
P(S') = 1 - P(S) ≈ 97% (probability a single random pair
is not common)
Let T be the event where
all consecutive pairs of words in a list of 12 words are
not common.
P(T) = P(S'
1 ∩ S'
2 ∩ ... ∩ S'
11)
P(T) = P(S')
11 ≈ 77% (probability that
all 11 consecutive pairs of an Electrum 12-word seed are
not common)
P(T') = 1 - P(T) ≈
23% (probability that at least one of the 11 pairs of an Electrum seed is common)So there's an
almost 1 in 4 chance that a randomly generated Electrum seed will have a pair of adjacent words on the 1,000,000 most common list. Since that list isn't all that big (for comparison, it includes "green screen" but not "velvel cage" nor "nerd paradise"), it's probably even more likely that a random seed contains uncommon but grammatically correct (and sensical) pairs of words like "nerd paradise".