The translator into Welsh was T Gwynn Jones 1871-1949, an outstanding poet in traditional and modern forms of poetry in Welsh: see a biographical essay on him in the Dictionary of Welsh Biography
Source: https://www.angelfire.com/in/gillionhome/Lyrics/Caneuon/SafaiRFam.html
The English version of the Welsh is by Richard B Gillion (2020).

Safai’r fam yn drist gan wylo, Wrth y groes, a gwasgu dwylo, Weld ei mab ar bren y groes. Trwy ei henaid drist, tosturus, A hi yno yn ddolurus, Gwanai’r cledd ag ingol loes.	The mother sadly stood weeping, By the cross, wringing her hands, Seeing her son on the wood of the cross. Through her sad, pitiful soul, And she there doleful, The sword weakened with agonising anguish.
O mor drist, O mor boeniedig Ydoedd hi, y fendigedig, Mam yr Unmab ar y pren! Yno safai a dolefai Wrth ei wylio lle dioddefai Boenau blin gan blygu’i ben.	O how sad, O how pained Was she, the blessed one, Mother of the only son on the tree! There she stood and lamented As she watched the place he suffered Grievous pains as he bowed his head.
Pwy na wylai, ar a aned, Weled yno cyn druaned Fam yr Iesu yn ei chur? Pa ryw galon nad ymchwelai Wylio yno’r fam a welai Boeni mab ei mynwes bur?	Who would not weep, of anyone born, Seeing there so wretched The mother of Jesus in her pain? What kind of heart would not swell Watching there the mother who saw Suffering pain, the son of her pure bosom?
Dros yr eiddo a’u pechodau Hi a’i gwelai dan ddyrnodau Ac arteithiau ar y pren. Gwyliai roi ei mab tirionaf I farwolaeth, oedd greulonaf, Ac yn angau’n plygu’i ben.	For his own and their sins She saw him under the blows And tortures on the tree. She watched them put her tenderest son To a death, that was the most cruel, And in death bowing his head.
Fam dirionaf, ffynnon cariad, Fel y gwypwyf gydalariad Pâr im deimlo grym y loes; Pâr i’m calon drachynhesu Ato ef, fy Nuw, fy Iesu, Fel y rhoddwyf iddo f’oes.	Tenderest Mother, the fount of love, That I may share thy lamentation Cause me to feel the force of thy anguish; Cause my heart to warm again Towards him, my God, my Jesus, That I may give to him my lifespan.
Fam sancteiddiaf, boed i’m calon Gyd-ddioddef ei dreialon Ef pan grogai ar y groes. Boed i mi â’th Unmab gwirion Ran o’r hyn a ddug mor dirion Erof i â dirfawr loes.	Holiest Mother, may my heart be Sharing in the suffering of his trials When he was hanging on the cross. May I and thy innocent only son be Part of that which he bore so tenderly For my sake with enormous anguish.