What's the relevance of these bash completion suggestions?

~ is $HOME. For me, cd ~ is /home/cat. Simple so far, yes?

In Bash, the following happens:

cat @ mint-kitty : ~/Downloads $ cd ~ # from /home/cat/Downloads to /home/cat/, as an example, but behaviour happens with any directory cat @ mint-kitty : ~ $ cd ~<TAB>proxy/ # oh? what's this? cat @ mint-kitty : /bin $ cd ~<TAB><TAB> ~ais ~clamav/ ~debian-tor/ ~gitlog ~list ~mixmaster/ ~ntp ~redis/ ~stunnel4 ~systemd-resolve ~uuidd/ ~avahi/ ~cl-builder/ ~dirmngr/ ~gnats ~lp ~monkeysphere/ ~oident/ ~roard/ ~sync/ ~systemd-timesync/ ~vde2-net ~avahi-autoipd/ ~clickpkg ~dnsmasq/ ~irc ~mail/ ~mpd/ ~pdnsd/ ~root/ ~syncache/ ~timidity/ ~whoopsie ~backup/ ~colord/ ~epmd ~jetty/ ~man/ ~muroard/ ~postgres/ ~rtkit/ ~sys/ ~tomcat8 ~www-data/ ~bin/ ~daemon/ ~festival ~libvirt-dnsmasq/ ~mdm/ ~mysql ~proxy/ ~saned ~syslog ~trafficserver ~bind/ ~Debian-exim/ ~games/ ~libvirt-qemu/ ~memcache ~news ~pulse ~speech-dispatcher ~systemd-bus-proxy/ ~uml-net ~cat/ ~debian-spamd/ ~gitdaemon ~lightdm/ ~messagebus/ ~nobody ~radvd ~sshd/ ~systemd-network ~uucp cat @ mint-kitty : /bin $ cd ~systemd-resolve bash: cd: /run/systemd/resolve: No such file or directory 1 | cat @ mint-kitty : /bin $ cd ~redis cat @ mint-kitty : /var/lib/redis $ cd ~clamav cat @ mint-kitty : /var/lib/clamav $ cd ~irc bash: cd: /var/run/ircd: No such file or directory 1 | cat @ mint-kitty : /var/lib/clamav $ cd ~gnats bash: cd: /var/lib/gnats: No such file or directory 1 | cat @ mint-kitty : /var/lib/clamav $ cd ~sshd cat @ mint-kitty : /var/run/sshd $ cd ~nobody bash: cd: /nonexistent: No such file or directory 

^{Obviously, <TAB> represents the TAB key sending the byte at ASCII 9, not that actual text.}

I've left in my PS1 prompt to show the current path and the return codes. My question is, what's the relevance of these directories being autocompleted from ~?

I've created a table of these and where they point, to better understand them (but I'm just more confused now).

thing points-at? =========================================== ~ais ENOENT /home/ais/ # user ais uid=156(ais) gid=163(ais) groups=163(ais) does not have an entry in /home/ ~avahi /var/run/avahi-daemon/ ~avahi-autoipd /var/lib/avahi-autoipd/ ~backup /var/backups/ ~bin /bin/ ~bind /var/cache/bind/ ~cat /home/cat/ ~clamav /var/lib/clamav/ ~cl-builder /usr/share/common-lisp// # two slashes ~clickpkg ENOENT /nonexsistent/ # yes, really ~colord /var/lib/colord/ ~daemon /usr/sbin/ # ?? ~Debian-exim /var/spool/exim4/ # ?? ~debian-spamd /var/lib/spamassassin/ ~debian-tor /var/lib/tor/ ~dirmngr /var/cache/dirmngr/ ~dnsmasq /var/lib/misc/ # ?? ~epmd /var/run/epmd/ ~festival ENOENT /home/festival # user festival uid=131(festival) gid=29(audio) groups=29(audio) does not have an entry in /home/ ~games /usr/games/ # ??? ~gitdaemon ENOENT /nonexistent/ ~gitlog ENOENT /nonexistent/ ~gnats /var/lib/ircd/ ~jetty /usr/share/jetty8/ ~libvirt-dnsmasq /var/lib/libvirt/ ~libvirt-qemu /var/lib/libvirt/ ~lightdm /var/lib/lightdm/ ~list ENOENT /var/list/ ~lp ENOENT /var/spool/lpd/ ~mail /var/mail/ ~man /var/cache/man/ ~mdm /var/lib/mdm/ ~memcache ENOENT /nonexistent/ ~messagebus /var/run/dbus ~mixmaster /var/lib/mixmaster/ ~monkeysphere /var/lib/monkeysphere/ ~mpd /var/lib/mpd/ ~muroard /var/lib/muroard/ ~mysql ENOENT /nonexistent/ ~nobody ENOENT /nonexistent/ ~ntp ENOENT /home/ntp # user ntp uid=107(ntp) gid=114(ntp) groups=114(ntp) does not have an entry in /home/ ~oident / # ???? ~pdnsd /var/cache/pdnsd/ ~postgres /var/lib/postgresql/ ~proxy /bin/ ~pulse ENOENT /var/run/pulse ~radvd ENOENT /var/run/radvd ~redis /var/lib/redis ~roard /var/lib/roard ~root /root ~rtkit /proc ~saned ENOENT /var/lib/saned ~speech-dispatcher ENOENT /var/run/speech-dispatcher ~sshd /var/run/sshd ~stunnel4 ENOENT /var/run/stunnel4 ~sync /bin/ ~syncache /var/run/syncache-drb/ ~sys /dev/ # ??? ~syslog ENOENT /home/syslog # user syslog uid=104(syslog) gid=109(syslog) groups=109(syslog),4(adm) does not have an entry in /home/ ~systemd-bus-proxy /run/systemd/ ~systemd-network ENOENT /run/systemd/netif/ ~systemd-resolve ENOENT /run/systemd/resolve/ ~systemd-timesync /run/systemd/ ~timidity /etc/timidity/ ~tomcat8 ENOENT /usr/share/tomcat8/ ~trafficserver ENOENT /var/run/trafficserver/ ~uml-net ENOENT /home/uml-net/ # user uml-net uid=146(uml-net) gid=155(uml-net) groups=155(uml-net) does not have an entry in /home/ ~uucp ENOENT /var/spool/uucp/ ~uuidd /run/uuidd/ ~vde2-net ENOENT /var/run/vde2/ ~whoospie ENOENT /nonexistent/ ~www-data /var/www 

The thing column is the entry shown by ~<TAB><TAB>. points-at is either the directory thing points to, or the nonexistent place thing points to.

For instance, ~cat gives bash: /home/cat: Is a directory, so ~cat -> /home/cat but ~clickpkg gives bash: /nonexistent: No such file or directory, so ~clickpkg -> ENOENT /nonexistent/.

I've presented all the data I've got. What's going on here? Is ~ being secretly expanded to something?