In Ps.84:6 (ESV) it says:
The word in bold is sometimes taken to mean ‘weeping’, as in the ASV and NLT. Sometimes it is thought to refer to a plant that grew in the valley. The NET Bible (which, along with most versions, leaves the word untranslated) has the following footnote:
The translation assumes that the Hebrew phrase עֵמֶק הַבָּכָא (’emeq habbakha’) is the name of an otherwise unknown arid valley through which pilgrims to Jerusalem passed. The term בָּכָא (bakha’) may be the name of a particular type of plant or shrub that grew in this valley. O. Borowski (Agriculture in Iron Age Israel, 130) suggests it is the black mulberry. Some take the phrase as purely metaphorical and relate בָּכָא to the root בָּכָה (bakhah, “to weep”). In this case one might translate, “the valley of weeping” or “the valley of affliction.”
Personally, I find the translation ‘weeping’ most appealing. The psalm describes a journey to Jerusalem (Ps. 84:6-7) where God dwells in the temple (Ps. 84:2): as the people travelling towards God’s dwelling place face difficulties (as the travel through the ‘valley of weeping’ [cp. the ‘valley of the shadow of death’: Ps. 23:4]) they are refreshed by God so that they can endure and reach their destination (Ps. 84:7). This way, it’s possibly a picture of God helping his people to draw closer to him and to get to the kingdom.