Most of the cutesy sayings with Greek letters incorporated use what the letter LOOKS like, not what the letter sounds like/really represents. I know when DG is used, the Delta is often used where an "A" would be because they both look like triangles and the Gamma is usually an "r" -- like these:
For Theta Alpha, I'd use an "O" for Theta, and an "A" for Alpha - despite them not quite having the same sound, etc.
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There are friends who pass like ships in the night, who meet for a moment, then sail out of sight, with never a backward glance of regret...Friends we meet briefly then quickly forget.
Then there are friends who sail together, through quiet waters and stormy weather. Helping each other through joy and through strife. And those are the kind who give meaning to life.
~ ⚓ΔΓ⚓ ~