An nTOH (pronounced /toʊ/, like "toe") stands for the nth tritave of odd harmonics.
TOHs reject factors of 2 in JI ratios, having a prime minimum of 3 (similar to BohlenPierce).
It is similar in concept to an octave of the harmonic series, a special case of a mode of the harmonic series where the mode is a power of 2. However, here the tuning spans (and repeats at) the tritave, and includes only odds.
1TOH
step

0

1

pitch

(1/1)

3/1

reduced

(1/1)

3/1

2TOH
step

0

1

2

3

pitch

(3/3)

5/3

7/3

9/3

reduced

(1/1)

5/3

7/3

3/1

3TOH
step

0

1

2

3

4

5

6

7

8

9

pitch

(9/9)

11/9

13/9

15/9

17/9

19/9

21/9

23/9

25/9

27/9

reduced

(1/1)

11/9

13/9

5/3

17/9

19/9

7/3

23/9

25/9

3/1

Listening
https://soundcloud.com/cmloegcmluin/sets/thirdtritaveoddharmonics