Gynna i is to be recommended for students of Gog - it’s very common. They have simply generalised the stem gynn- and added the standard endings.
gynno fo
gynni hi
gynnon ni
gynnoch chi
gynnyn nhw
Clever gogs!
(Although note that for ti they do usually say gen ti rather than gynnat ti, in my experience at least…)
Diolch yn fawr Gareth. Actually, in the aforementioned dictionary, you offer the form “gyn ti” for Gogs, and it helped me to recall that on that excellent programme from the land of Gog go iawn, Rownd a Rownd, I had heard people (especially Matthew Parry) saying “gyn ti” and “gyn i”.
However, in my ignorance (or innocence), I had visualised this as being spelt “gin” (and I can’t remember how the Welsh subtitles would have spelt it, but likely they would have gone with “gen”).
And of course, the pronunciation of the “y” differs between its use in “gynna i” and “gyn i”
(and not having grown up with a North Walian ear, I would not be able to distinguish between the sound of “gyn” and “gin”).
Although gynno fo and gynni hi are nice and consistent in your list above, I personally rather like “ganddo fo” and “ganddi hi”, for some reason. 
(I think it’s what they taught on the original SSiW Courses - Not sure about the later Levels).
Oh yes - both very common as well. 
Curiously enough, I noticed another variation on tonight’s episode (28 Chwefror 2019):
https://www.s4c.cymru/clic/programme/799631108
At about 3.54, the character Jason says:
(According to the subtitle):
“Fafr gynno fi i ofyn i chdi”
(“I have a favour to ask you”).
It’s a berserk free-for-all out there, isn’t it?
How I love chaos.
This might be why the English accuse Welsh of being a “made-up language”!
I think you may be going a bit far when you say ‘the English’ there… 
Thanks for all the help with gynna i! I really should get a copy of one these brilliant Gareth King books
Don’t delay - Buy one today! 
Or indeed why stop at one? Remember the old capitalist line:
Why settle for one, when for just double the price you could have two!
Gareth,
Do keep an eye out for Antipodean freight-outs…
Not really a question more an observation. I watched the Netflix (other Internet film providers are available) film The Outlaw King about Robert the Bruce. This got me reading about Robert and his murder of his rival in a church. According to contemporary sources he came out of the church and said to his mate he wasn’t sure if he’d killed him. Roger de Fitzpatrick is meant to have said “I mak sikker” (I’ll make sure).
Is this bit of Scots likely to be related to “sicr”?
Sorry, slightly out of left field on this post 
Yes, sounds like you are spot on, Anthony.
According to the Scots Glossary, Sikker seems to have the same meaning as Sicr: Safe, secure, sure, etc.
I was guessing that it came from Cumbric. But then I noticed that it is also Danish. Sure certain sure-fire unfaltering. So perhaps it came from a Norse word.
That is interesting!
I suspect it’s Latin, as in English ‘secure’ – but seems to have been borrowed quite widely, early enough to become nativized throughout – I’m thinking of German sicher, etc. as well. And then in French the -c- sound goes via a -g- and then effectively soft-mutates and disappears, so you’re left with sûr/‘sure’/siwr.
(Also, according to the GPC, segur, which – weirdly – mostly seems to mean ‘idle’.)
Ah, right, thanks. I’ve seen that on out-of-use speed cameras.
Fitting in with your comment, Sikker (in English) is given as a former version of secure.
Cwestiwn gyflym go iawn oddi wrthaf fi am unwaith! Pa air fyddwch chi’n defnyddio’r ar gyfer “ABC Illustration Cyf/Ltd” yn Gymraeg? Dwi wedi gofyn fy ffrind ond so hi ddim yn gwybod heblaw “Eglureb”. Hefyd, mae hi’n meddwl so hynny’n swno’n naturiol tho!
A real quick question from me for once! Which word would you use for “ABC Illustration Cyf/Ltd” yn Gymraeg? I’ve asked my friend on she doesn’t know except “Eglureb”. Also, she thinks that doesn’t sound natural though!
(I might have lied about it being quick! 
)
Do you mean Illustration as in pictures, graphic design, etc? How about Darlun?
Darlun did cross my mind, as well as my friend, although in this case there’s a subtle distinction between drawing/arlunio and illustration, at least in English anyway! It’s specifically illustrating with drawings/paintings but not the act/doing, just the description; “an illustration” “ABC’s Illustration” “ABC Illustration Ltd” etc if that helps at all!
