Tell me the Lunar Phase!
Node.js, 145 bytes
p=&gt;'third/waning/first/full/waxing/new'.split`/`[(s=require('fs').statSync(p).size)%418%6]+' '+'quarter/crescent/gibbous/moon'.split`/`[s%12%9%4]

Try it online! (generates dummy files with the same sizes)
How?
We just look at the size of the file and convert it to indices in two lookup tables.
First part:
 phase | file size | mod 418 | mod 6 | mapped to
-------+-----------+---------+-------+-----------
   0   |    3451   |    107  |    5  | new
   1   |    6430   |    160  |    4  | waxing
   2   |    5144   |    128  |    2  | first
   3   |    7070   |    382  |    4  | waxing
   4   |    5283   |    267  |    3  | full
   5   |    7067   |    379  |    1  | waning
   6   |    4976   |    378  |    0  | third
   7   |    6337   |     67  |    1  | waning

Second part:
 phase | file size | mod 12 |  mod 9 |  mod 4 | mapped to
-------+-----------+--------+--------+--------+-----------
   0   |    3451   |     7  |     7  |    3   | moon
   1   |    6430   |    10  |     1  |    1   | crescent
   2   |    5144   |     8  |     8  |    0   | quarter
   3   |    7070   |     2  |     2  |    2   | gibbous
   4   |    5283   |     3  |     3  |    3   | moon
   5   |    7067   |    11  |     2  |    2   | gibbous
   6   |    4976   |     8  |     8  |    0   | quarter
   7   |    6337   |     1  |     1  |    1   | crescent